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Small Animal Ophthalmic Atlas and Guide

Small Animal Ophthalmic Atlas and Guide

Christine C Lim DVMDiplomate of the American College of Veterinary OphthalmologistsAssistant professor of ophthalmologyUniversity of Minnesota College of Veterinary MedicineSt Paul MN USA

This edition first published 2015 copy 2015 by John Wiley amp Sons Inc

Editorial Offices1606 Golden Aspen Drive Suites 103 and 104 Ames Iowa 50014-8300 USAThe Atrium Southern Gate Chichester West Sussex PO19 8SQ UK9600 Garsington Road Oxford OX4 2DQ UK

For details of our global editorial offices for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at wwwwileycomwiley-blackwell

Authorization to photocopy items for internal or personal use or the internal or personal use of specific clients is granted by Blackwell Publishing provided that the base fee is paid directly to the Copyright Clearance Center 222 Rosewood Drive Danvers MA 01923 For those organizations that have been granted a photocopy license by CCC a separate system of payments has been arranged The fee codes for users of the Transactional Reporting Service are ISBN-13 978-1-1186-8976-92015

Designations used by companies to distinguish their products are often claimed as trademarks All brand names and product names used in this book are trade names service marks trademarks or registered trademarks of their respective owners The publisher is not associated with any product or vendor mentioned in this book

The contents of this work are intended to further general scientific research understanding and discussion only and are not intended and should not be relied upon as recommending or promoting a specific method diagnosis or treatment by health science practitioners for any particular patient The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties including without limitation any implied warranties of fitness for a particular purpose In view of ongoing research equipment modifications changes in governmental regulations and the constant flow of information relating to the use of medicines equipment and devices the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine equipment or device for among other things any changes in the instructions or indication of usage and for added warnings and precautions Readers should consult with a specialist where appropriate The fact that an organization or Website is referred to in this work as a citation andor a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make Further readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read No warranty may be created or extended by any promotional statements for this work Neither the publisher nor the author shall be liable for any damages arising herefrom

Library of Congress Cataloging-in-Publication Data applied for

A catalogue record for this book is available from the British Library

Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic books

Set in 9512pt Minion by SPi Publisher Services Pondicherry India

1 2015

To those who made this book possible my colleagues mentors students patients and of course my family

vii

Contents

Preface xList of abbreviations xiGlossary xii

Section I Atlas 1

1 Orbit 3Clinical signs associated with orbital neoplasia 3Clinical signs associated with orbital cellulitis 3Enophthalmos 4Brachycephalic ocular syndrome 4Ventromedial entropion associated with brachycephalic

ocular syndrome 4Clinical signs associated with Hornerrsquos syndrome 5Clinical signs associated with Hornerrsquos syndrome 5Appearance of Hornerrsquos syndrome following application of

sympathomimetic drugs 5Clinical signs associated with orbital neoplasia 6Clinical signs associated with proptosis 6

2 Eyelids 7Normal appearance of punctum 7Ectopic cilia 7Distichiae 8Distichiae 8Ectopic cilia and chalazion 8Lower eyelid entropion due to conformation 9Facial trichiasis 9Eyelid agenesis 9Appearance of entropion after temporary correction

using tacking sutures 10Lower eyelid ectropion 10Meibomian adenoma 10Meibomian adenoma 11Eyelid melanocytoma 11Chalazion 11Blepharitis 12Blepharitis 12Blepharitis 12

3 Third eyelid nasolacrimal system and precorneal tear film 13Pathologic changes to the third eyelid associated with

pannus 13

Scrolled third eyelid cartilage 13Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Superficial neoplasia of the third eyelid 14Neoplasia of the third eyelid gland 15Positive Jones test ndash appearance of fluorescein

in mouth 15Positive Jones test ndash appearance of fluorescein

at nostril 15

4 Conjunctiva 16Normal appearance of the conjunctiva 16Conjunctival hyperemia 16Chemosis and conjunctival hyperemia 17Chemosis 17Conjunctival follicles 17Conjunctival thickening associated with infiltrative

neoplasia 18Superficial conjunctival neoplasia 18Subconjunctival hemorrhage 18Conjunctival follicles 19Superficial conjunctival neoplasia 19Conjunctival neoplasia 19

5 Cornea 20Superficial corneal vascularization associated with

keratoconjunctivitis sicca 20Appearance of a dry cornea with concurrent anterior

uveitis 20Typical appearance of superficial corneal vessels 21Typical appearance of deep corneal vessels 21Typical appearance of corneal edema 21Corneal melanosis 22Typical melanin distribution associated with pigmentary

keratitis 22Typical appearance of corneal fibrosis with concurrent

corneal vascularization 22Corneal white cell infiltrate with concurrent corneal

vascularization and edema 23Corneal deposits associated with corneal dystrophy 23Corneal deposits associated with corneal dystrophy 23Corneal mineral deposits 24Typical changes associated with keratoconjunctivitis

sicca 24

viii Contents

Predominantly melanotic corneal changes associated with pannus 24

Predominantly fibrovascular corneal changes associated with pannus 25

Corneal changes associated with pannus mixture of melanosis and fibrovascular changes 25

Superficial corneal ulcer 25Indolent corneal ulcer with fluorescein stain applied 26Indolent corneal ulcer prior to fluorescein stain 26Indolent corneal ulcer after fluorescein stain 26Deep corneal ulcer 27Descemetocele after application of fluorescein stain 27Descemetocele after application of fluorescein stain

viewed with cobalt blue light 27Corneal perforation with iris prolapse 28Corneal perforation with iris prolapse and hyphema 28Corneal perforation with large iris prolapse 28Melting corneal ulcer 29Perforated melting corneal ulcer 29Dendritic corneal ulcers 29Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Corneal sequestrum light brown with minimal

keratitis 31Corneal sequestrum dark brown with moderate

keratoconjunctivitis 31Corneal sequestrum dark brown with significant

keratoconjunctivitis 31

6 Anterior uvea 32Iris-to-cornea persistent pupillary membranes 32Iris-to-iris persistent pupillary membranes 32Posterior synechiae 33Anterior chamber uveal cysts 33Anterior chamber uveal cysts 33Transillumination of posterior chamber uveal cysts 34Iris atrophy 34Iris atrophy 34Severe iris atrophy 35Focal iris hyperpigmentation 35Feline diffuse iris melanoma 35Feline diffuse iris melanoma 36Canine melanocytoma 36Canine melanocytoma 36Canine ciliary body adenoma 37Clinical signs of uveitis chemosis episcleral

congestion deep corneal vascularization and diffuse corneal edema 37

Aqueous flare 37Keratic precipitates 38Hypopyon with concurrent corneal ulceration 38Hyphema 38Rubeosis iridis 39Iris thickening 39

Posterior synechia 39Iris bombeacute 40

7 Lens 41Nuclear sclerosis 41Nuclear sclerosis 41Incipient cataract 42Incipient cataract 42Incomplete cataract 42Incomplete cataract 43Incomplete cataract 43Complete cataract 43Complete resorbing cataract 44Incomplete resorbing cataract 44Lens subluxation 44Lens subluxation 45Anterior lens luxation 45Posterior lens luxation 45

8 Posterior segment 46Normal canine fundus 46Normal canine fundus 46Normal feline fundus 47Subalbinotic atapetal canine fundus 47Subalbinotic feline fundus 47Tapetal hyperreflectivity and retinal vascular attenuation

in a cat 48Tapetal hyperreflectivity and retinal vascular attenuation

in a dog 48Focal retinal degenerationchorioretinal scar 48Focal retinal degenerationchorioretinal scar 49Tapetal hyporeflectivity due to hypertensive

retinopathy 49Tapetal hyporeflectivity 49Tapetal hyporeflectivity 50Fluid and white cell infiltrate in the nontapetal fundus

(chorioretinitis) 50Focal white cell infiltrate (chorioretinitis) and retinal

degeneration in the nontapetal fundus 50Multifocal retinal degeneration in the nontapetal

fundus 51Hemorrhage in the nontapetal fundus 51Hemorrhage in the tapetal fundus 51Serous retinal detachment and retinal hemorrhage due to

hypertensive retinopathy 52External view of serous retinal detachment 52Serous retinal detachment 52Rhegmatogenous retinal detachment 53Optic nerve atrophydegeneration - mild 53Optic nerve atrophydegeneration - severe 53Optic disc cupping in an atapetal fundus 54Optic disc cupping 54Optic neuritis 54Optic neuritis 55Asteroid hyalosis 55

Contents ix

Choroidal hypoplasia (collie eye anomaly) 55Posterior polar coloboma and choroidal hypoplasia

(collie eye anomaly) in a subalbinotic fundus 56

9 Glaucoma 57Typical appearance of acute glaucoma 57Haabrsquos striae 57

Section II Guide 59

10 Orbit 61Diseases of the orbit 62Brachycephalic ocular syndrome 62Hornerrsquos syndrome 63Orbital cellulitis and abscess 65Orbital neoplasia 67Proptosis 68Further reading 70References 70

11 Eyelids 71Diseases of the eyelid 72Distichiasis 72Ectopic cilia 73Trichiasis 73Eyelid agenesis 75Entropion 75Ectropion 77Eyelid neoplasia 78Chalazion 79Blepharitis 80Eyelid laceration 81Further reading 82References 82

12 The third eyelid nasolacrimal system and precorneal tear film 83Diseases of the third eyelid and lacrimal system 84Third eyelid gland prolapse (ldquocherry eyerdquo) 84Third eyelid neoplasia 85Nasolacrimal duct obstruction 87Tear film disordersmdashKCS 88Qualitative tear film abnormality 88References 90

13 Conjunctiva 91Diseases of conjunctiva 91Canine conjunctivitis 91Feline conjunctivitis 93Conjunctival neoplasia 95Further reading 96References 97

14 Cornea 98Corneal diseases 99Corneal dystrophy 99

Canine keratitis 100Keratoconjunctivitis sicca (KCS) 101Pigmentary keratitis 103Pannuschronic superficial keratitis 104Corneal ulceration 105Simple corneal ulceration 105Indolent corneal ulceration 106Deep and perforating corneal ulceration 108Melting corneal ulceration 110Feline keratitis nonulcerative and ulcerative 111Feline eosinophilic keratoconjunctivitis (EK) 112Corneal sequestrum 113Further reading 114References 114

15 Anterior uvea 116Anterior uveal diseases 116Persistent pupillary membranes (PPMs) 116Uveal cysts 117Iris atrophy 118Feline diffuse iris melanoma 118Canine anterior uveal melanocytic neoplasia 119Iridociliary neoplasia 120Anterior uveitis 121Further reading 124References 124

16 Lens 125Diseases of the lens 125Nuclear sclerosis 125Cataract 126Lens subluxation and luxation 128Further reading 129References 130

17 Posterior segment 131Diseases of the posterior segment 133Asteroid hyalosis 133Collie eye anomaly 133Progressive retinal atrophy (PRA) 134Sudden acquired retinal degeneration syndrome

(SARDS) 135Retinal degeneration (excluding PRA and SARDS) 136Chorioretinitis 137Retinal detachment 138Hypertensive retinopathy 140Optic neuritis 141Further reading 142References 142

18 Glaucoma 144Glaucoma 144Further reading 148References 148

Index 149

x

Preface

Small animal general practice is a high-paced profession that requires the veterinarian to arrive at a diagnosis and formulate diagnostic and therapeutic plans within a 15- to 20-minute appointment window As a general practitioner I often found myself in this position When I did I wished for a reference where I could find a photograph similar to what I observed in the patient along with enough information to implement a plan for treatment Such scenarios provided the idea for this book The Small Animal Ophthalmic Atlas and Guide is designed as a handy reference for the busy general practitioner The bookrsquos goals are to (i) provide an extensive collection of images that practitioners can use to obtain a diagnosis during an outpatient appointment and (ii) provide just enough information about each disease relevant diagnostic tests and treatment to allow for development of a medically sound management plan

The majority of ophthalmic conditions selected for inclusion in this book are those that present frequently in general practice A smaller number of less common conditions are also included because of their significant impact on vision andor overall health of the eye The purpose of this book is not to describe every known small animal ophthalmic disease nor is it intended

to be an exhaustive review of the diseases included in the book Because this is intended to be a quick reference each chapter includes only enough background information to facilitate discussion of each ocular disease most of the information is designed to support immediate management and only select procedures are detailed step-by-step (For example detailed directions for ocular surgeries should be sought from other texts) As a guide for those who wish to delve more deeply into specific ophthalmic conditions each chapter contains a list of suggestions for further reading

Of course no reference book can be a substitute for up-to-date education sound clinical judgment and the practitionerrsquos individual knowledge of a particular patient Readers of this book should always think critically about the cases presenting to them seek advice from and make referrals to veterinary oph-thalmologists when expert care is warranted and verify that new research or information from manufacturers has not eclipsed the information in this text My hope is that this book will make it easier for practitioners to handle ophthalmic cases in their daily practice

Christine C Lim

xi

List of abbreviations

CBC complete blood countCsA cyclosporine ACT computed tomographyDNA deoxyribonucleic acidDSH domestic shorthairERG electroretinogramFeLV feline leukemia virusFIP feline infectious peritonitisFHV-1 feline herpesvirusFIV feline immunodeficiency virusIOP intraocular pressureIV intravenous

KCS keratoconjunctivitis siccaLIU lens-induced uveitisMRI magnetic resonance imagingNSAID nonsteroidal anti-inflammatory drugPLR pupillary light reflexPO by mouthPPM persistent pupillary membranePRA progressive retinal atrophyRPE retinal pigmented epitheliumSARDS sudden acquired retinal degeneration

syndromeSTT Schirmer tear test

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

Small Animal Ophthalmic Atlas and Guide

Small Animal Ophthalmic Atlas and Guide

Christine C Lim DVMDiplomate of the American College of Veterinary OphthalmologistsAssistant professor of ophthalmologyUniversity of Minnesota College of Veterinary MedicineSt Paul MN USA

This edition first published 2015 copy 2015 by John Wiley amp Sons Inc

Editorial Offices1606 Golden Aspen Drive Suites 103 and 104 Ames Iowa 50014-8300 USAThe Atrium Southern Gate Chichester West Sussex PO19 8SQ UK9600 Garsington Road Oxford OX4 2DQ UK

For details of our global editorial offices for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at wwwwileycomwiley-blackwell

Authorization to photocopy items for internal or personal use or the internal or personal use of specific clients is granted by Blackwell Publishing provided that the base fee is paid directly to the Copyright Clearance Center 222 Rosewood Drive Danvers MA 01923 For those organizations that have been granted a photocopy license by CCC a separate system of payments has been arranged The fee codes for users of the Transactional Reporting Service are ISBN-13 978-1-1186-8976-92015

Designations used by companies to distinguish their products are often claimed as trademarks All brand names and product names used in this book are trade names service marks trademarks or registered trademarks of their respective owners The publisher is not associated with any product or vendor mentioned in this book

The contents of this work are intended to further general scientific research understanding and discussion only and are not intended and should not be relied upon as recommending or promoting a specific method diagnosis or treatment by health science practitioners for any particular patient The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties including without limitation any implied warranties of fitness for a particular purpose In view of ongoing research equipment modifications changes in governmental regulations and the constant flow of information relating to the use of medicines equipment and devices the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine equipment or device for among other things any changes in the instructions or indication of usage and for added warnings and precautions Readers should consult with a specialist where appropriate The fact that an organization or Website is referred to in this work as a citation andor a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make Further readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read No warranty may be created or extended by any promotional statements for this work Neither the publisher nor the author shall be liable for any damages arising herefrom

Library of Congress Cataloging-in-Publication Data applied for

A catalogue record for this book is available from the British Library

Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic books

Set in 9512pt Minion by SPi Publisher Services Pondicherry India

1 2015

To those who made this book possible my colleagues mentors students patients and of course my family

vii

Contents

Preface xList of abbreviations xiGlossary xii

Section I Atlas 1

1 Orbit 3Clinical signs associated with orbital neoplasia 3Clinical signs associated with orbital cellulitis 3Enophthalmos 4Brachycephalic ocular syndrome 4Ventromedial entropion associated with brachycephalic

ocular syndrome 4Clinical signs associated with Hornerrsquos syndrome 5Clinical signs associated with Hornerrsquos syndrome 5Appearance of Hornerrsquos syndrome following application of

sympathomimetic drugs 5Clinical signs associated with orbital neoplasia 6Clinical signs associated with proptosis 6

2 Eyelids 7Normal appearance of punctum 7Ectopic cilia 7Distichiae 8Distichiae 8Ectopic cilia and chalazion 8Lower eyelid entropion due to conformation 9Facial trichiasis 9Eyelid agenesis 9Appearance of entropion after temporary correction

using tacking sutures 10Lower eyelid ectropion 10Meibomian adenoma 10Meibomian adenoma 11Eyelid melanocytoma 11Chalazion 11Blepharitis 12Blepharitis 12Blepharitis 12

3 Third eyelid nasolacrimal system and precorneal tear film 13Pathologic changes to the third eyelid associated with

pannus 13

Scrolled third eyelid cartilage 13Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Superficial neoplasia of the third eyelid 14Neoplasia of the third eyelid gland 15Positive Jones test ndash appearance of fluorescein

in mouth 15Positive Jones test ndash appearance of fluorescein

at nostril 15

4 Conjunctiva 16Normal appearance of the conjunctiva 16Conjunctival hyperemia 16Chemosis and conjunctival hyperemia 17Chemosis 17Conjunctival follicles 17Conjunctival thickening associated with infiltrative

neoplasia 18Superficial conjunctival neoplasia 18Subconjunctival hemorrhage 18Conjunctival follicles 19Superficial conjunctival neoplasia 19Conjunctival neoplasia 19

5 Cornea 20Superficial corneal vascularization associated with

keratoconjunctivitis sicca 20Appearance of a dry cornea with concurrent anterior

uveitis 20Typical appearance of superficial corneal vessels 21Typical appearance of deep corneal vessels 21Typical appearance of corneal edema 21Corneal melanosis 22Typical melanin distribution associated with pigmentary

keratitis 22Typical appearance of corneal fibrosis with concurrent

corneal vascularization 22Corneal white cell infiltrate with concurrent corneal

vascularization and edema 23Corneal deposits associated with corneal dystrophy 23Corneal deposits associated with corneal dystrophy 23Corneal mineral deposits 24Typical changes associated with keratoconjunctivitis

sicca 24

viii Contents

Predominantly melanotic corneal changes associated with pannus 24

Predominantly fibrovascular corneal changes associated with pannus 25

Corneal changes associated with pannus mixture of melanosis and fibrovascular changes 25

Superficial corneal ulcer 25Indolent corneal ulcer with fluorescein stain applied 26Indolent corneal ulcer prior to fluorescein stain 26Indolent corneal ulcer after fluorescein stain 26Deep corneal ulcer 27Descemetocele after application of fluorescein stain 27Descemetocele after application of fluorescein stain

viewed with cobalt blue light 27Corneal perforation with iris prolapse 28Corneal perforation with iris prolapse and hyphema 28Corneal perforation with large iris prolapse 28Melting corneal ulcer 29Perforated melting corneal ulcer 29Dendritic corneal ulcers 29Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Corneal sequestrum light brown with minimal

keratitis 31Corneal sequestrum dark brown with moderate

keratoconjunctivitis 31Corneal sequestrum dark brown with significant

keratoconjunctivitis 31

6 Anterior uvea 32Iris-to-cornea persistent pupillary membranes 32Iris-to-iris persistent pupillary membranes 32Posterior synechiae 33Anterior chamber uveal cysts 33Anterior chamber uveal cysts 33Transillumination of posterior chamber uveal cysts 34Iris atrophy 34Iris atrophy 34Severe iris atrophy 35Focal iris hyperpigmentation 35Feline diffuse iris melanoma 35Feline diffuse iris melanoma 36Canine melanocytoma 36Canine melanocytoma 36Canine ciliary body adenoma 37Clinical signs of uveitis chemosis episcleral

congestion deep corneal vascularization and diffuse corneal edema 37

Aqueous flare 37Keratic precipitates 38Hypopyon with concurrent corneal ulceration 38Hyphema 38Rubeosis iridis 39Iris thickening 39

Posterior synechia 39Iris bombeacute 40

7 Lens 41Nuclear sclerosis 41Nuclear sclerosis 41Incipient cataract 42Incipient cataract 42Incomplete cataract 42Incomplete cataract 43Incomplete cataract 43Complete cataract 43Complete resorbing cataract 44Incomplete resorbing cataract 44Lens subluxation 44Lens subluxation 45Anterior lens luxation 45Posterior lens luxation 45

8 Posterior segment 46Normal canine fundus 46Normal canine fundus 46Normal feline fundus 47Subalbinotic atapetal canine fundus 47Subalbinotic feline fundus 47Tapetal hyperreflectivity and retinal vascular attenuation

in a cat 48Tapetal hyperreflectivity and retinal vascular attenuation

in a dog 48Focal retinal degenerationchorioretinal scar 48Focal retinal degenerationchorioretinal scar 49Tapetal hyporeflectivity due to hypertensive

retinopathy 49Tapetal hyporeflectivity 49Tapetal hyporeflectivity 50Fluid and white cell infiltrate in the nontapetal fundus

(chorioretinitis) 50Focal white cell infiltrate (chorioretinitis) and retinal

degeneration in the nontapetal fundus 50Multifocal retinal degeneration in the nontapetal

fundus 51Hemorrhage in the nontapetal fundus 51Hemorrhage in the tapetal fundus 51Serous retinal detachment and retinal hemorrhage due to

hypertensive retinopathy 52External view of serous retinal detachment 52Serous retinal detachment 52Rhegmatogenous retinal detachment 53Optic nerve atrophydegeneration - mild 53Optic nerve atrophydegeneration - severe 53Optic disc cupping in an atapetal fundus 54Optic disc cupping 54Optic neuritis 54Optic neuritis 55Asteroid hyalosis 55

Contents ix

Choroidal hypoplasia (collie eye anomaly) 55Posterior polar coloboma and choroidal hypoplasia

(collie eye anomaly) in a subalbinotic fundus 56

9 Glaucoma 57Typical appearance of acute glaucoma 57Haabrsquos striae 57

Section II Guide 59

10 Orbit 61Diseases of the orbit 62Brachycephalic ocular syndrome 62Hornerrsquos syndrome 63Orbital cellulitis and abscess 65Orbital neoplasia 67Proptosis 68Further reading 70References 70

11 Eyelids 71Diseases of the eyelid 72Distichiasis 72Ectopic cilia 73Trichiasis 73Eyelid agenesis 75Entropion 75Ectropion 77Eyelid neoplasia 78Chalazion 79Blepharitis 80Eyelid laceration 81Further reading 82References 82

12 The third eyelid nasolacrimal system and precorneal tear film 83Diseases of the third eyelid and lacrimal system 84Third eyelid gland prolapse (ldquocherry eyerdquo) 84Third eyelid neoplasia 85Nasolacrimal duct obstruction 87Tear film disordersmdashKCS 88Qualitative tear film abnormality 88References 90

13 Conjunctiva 91Diseases of conjunctiva 91Canine conjunctivitis 91Feline conjunctivitis 93Conjunctival neoplasia 95Further reading 96References 97

14 Cornea 98Corneal diseases 99Corneal dystrophy 99

Canine keratitis 100Keratoconjunctivitis sicca (KCS) 101Pigmentary keratitis 103Pannuschronic superficial keratitis 104Corneal ulceration 105Simple corneal ulceration 105Indolent corneal ulceration 106Deep and perforating corneal ulceration 108Melting corneal ulceration 110Feline keratitis nonulcerative and ulcerative 111Feline eosinophilic keratoconjunctivitis (EK) 112Corneal sequestrum 113Further reading 114References 114

15 Anterior uvea 116Anterior uveal diseases 116Persistent pupillary membranes (PPMs) 116Uveal cysts 117Iris atrophy 118Feline diffuse iris melanoma 118Canine anterior uveal melanocytic neoplasia 119Iridociliary neoplasia 120Anterior uveitis 121Further reading 124References 124

16 Lens 125Diseases of the lens 125Nuclear sclerosis 125Cataract 126Lens subluxation and luxation 128Further reading 129References 130

17 Posterior segment 131Diseases of the posterior segment 133Asteroid hyalosis 133Collie eye anomaly 133Progressive retinal atrophy (PRA) 134Sudden acquired retinal degeneration syndrome

(SARDS) 135Retinal degeneration (excluding PRA and SARDS) 136Chorioretinitis 137Retinal detachment 138Hypertensive retinopathy 140Optic neuritis 141Further reading 142References 142

18 Glaucoma 144Glaucoma 144Further reading 148References 148

Index 149

x

Preface

Small animal general practice is a high-paced profession that requires the veterinarian to arrive at a diagnosis and formulate diagnostic and therapeutic plans within a 15- to 20-minute appointment window As a general practitioner I often found myself in this position When I did I wished for a reference where I could find a photograph similar to what I observed in the patient along with enough information to implement a plan for treatment Such scenarios provided the idea for this book The Small Animal Ophthalmic Atlas and Guide is designed as a handy reference for the busy general practitioner The bookrsquos goals are to (i) provide an extensive collection of images that practitioners can use to obtain a diagnosis during an outpatient appointment and (ii) provide just enough information about each disease relevant diagnostic tests and treatment to allow for development of a medically sound management plan

The majority of ophthalmic conditions selected for inclusion in this book are those that present frequently in general practice A smaller number of less common conditions are also included because of their significant impact on vision andor overall health of the eye The purpose of this book is not to describe every known small animal ophthalmic disease nor is it intended

to be an exhaustive review of the diseases included in the book Because this is intended to be a quick reference each chapter includes only enough background information to facilitate discussion of each ocular disease most of the information is designed to support immediate management and only select procedures are detailed step-by-step (For example detailed directions for ocular surgeries should be sought from other texts) As a guide for those who wish to delve more deeply into specific ophthalmic conditions each chapter contains a list of suggestions for further reading

Of course no reference book can be a substitute for up-to-date education sound clinical judgment and the practitionerrsquos individual knowledge of a particular patient Readers of this book should always think critically about the cases presenting to them seek advice from and make referrals to veterinary oph-thalmologists when expert care is warranted and verify that new research or information from manufacturers has not eclipsed the information in this text My hope is that this book will make it easier for practitioners to handle ophthalmic cases in their daily practice

Christine C Lim

xi

List of abbreviations

CBC complete blood countCsA cyclosporine ACT computed tomographyDNA deoxyribonucleic acidDSH domestic shorthairERG electroretinogramFeLV feline leukemia virusFIP feline infectious peritonitisFHV-1 feline herpesvirusFIV feline immunodeficiency virusIOP intraocular pressureIV intravenous

KCS keratoconjunctivitis siccaLIU lens-induced uveitisMRI magnetic resonance imagingNSAID nonsteroidal anti-inflammatory drugPLR pupillary light reflexPO by mouthPPM persistent pupillary membranePRA progressive retinal atrophyRPE retinal pigmented epitheliumSARDS sudden acquired retinal degeneration

syndromeSTT Schirmer tear test

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

Small Animal Ophthalmic Atlas and Guide

Christine C Lim DVMDiplomate of the American College of Veterinary OphthalmologistsAssistant professor of ophthalmologyUniversity of Minnesota College of Veterinary MedicineSt Paul MN USA

This edition first published 2015 copy 2015 by John Wiley amp Sons Inc

Editorial Offices1606 Golden Aspen Drive Suites 103 and 104 Ames Iowa 50014-8300 USAThe Atrium Southern Gate Chichester West Sussex PO19 8SQ UK9600 Garsington Road Oxford OX4 2DQ UK

For details of our global editorial offices for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at wwwwileycomwiley-blackwell

Authorization to photocopy items for internal or personal use or the internal or personal use of specific clients is granted by Blackwell Publishing provided that the base fee is paid directly to the Copyright Clearance Center 222 Rosewood Drive Danvers MA 01923 For those organizations that have been granted a photocopy license by CCC a separate system of payments has been arranged The fee codes for users of the Transactional Reporting Service are ISBN-13 978-1-1186-8976-92015

Designations used by companies to distinguish their products are often claimed as trademarks All brand names and product names used in this book are trade names service marks trademarks or registered trademarks of their respective owners The publisher is not associated with any product or vendor mentioned in this book

The contents of this work are intended to further general scientific research understanding and discussion only and are not intended and should not be relied upon as recommending or promoting a specific method diagnosis or treatment by health science practitioners for any particular patient The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties including without limitation any implied warranties of fitness for a particular purpose In view of ongoing research equipment modifications changes in governmental regulations and the constant flow of information relating to the use of medicines equipment and devices the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine equipment or device for among other things any changes in the instructions or indication of usage and for added warnings and precautions Readers should consult with a specialist where appropriate The fact that an organization or Website is referred to in this work as a citation andor a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make Further readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read No warranty may be created or extended by any promotional statements for this work Neither the publisher nor the author shall be liable for any damages arising herefrom

Library of Congress Cataloging-in-Publication Data applied for

A catalogue record for this book is available from the British Library

Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic books

Set in 9512pt Minion by SPi Publisher Services Pondicherry India

1 2015

To those who made this book possible my colleagues mentors students patients and of course my family

vii

Contents

Preface xList of abbreviations xiGlossary xii

Section I Atlas 1

1 Orbit 3Clinical signs associated with orbital neoplasia 3Clinical signs associated with orbital cellulitis 3Enophthalmos 4Brachycephalic ocular syndrome 4Ventromedial entropion associated with brachycephalic

ocular syndrome 4Clinical signs associated with Hornerrsquos syndrome 5Clinical signs associated with Hornerrsquos syndrome 5Appearance of Hornerrsquos syndrome following application of

sympathomimetic drugs 5Clinical signs associated with orbital neoplasia 6Clinical signs associated with proptosis 6

2 Eyelids 7Normal appearance of punctum 7Ectopic cilia 7Distichiae 8Distichiae 8Ectopic cilia and chalazion 8Lower eyelid entropion due to conformation 9Facial trichiasis 9Eyelid agenesis 9Appearance of entropion after temporary correction

using tacking sutures 10Lower eyelid ectropion 10Meibomian adenoma 10Meibomian adenoma 11Eyelid melanocytoma 11Chalazion 11Blepharitis 12Blepharitis 12Blepharitis 12

3 Third eyelid nasolacrimal system and precorneal tear film 13Pathologic changes to the third eyelid associated with

pannus 13

Scrolled third eyelid cartilage 13Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Superficial neoplasia of the third eyelid 14Neoplasia of the third eyelid gland 15Positive Jones test ndash appearance of fluorescein

in mouth 15Positive Jones test ndash appearance of fluorescein

at nostril 15

4 Conjunctiva 16Normal appearance of the conjunctiva 16Conjunctival hyperemia 16Chemosis and conjunctival hyperemia 17Chemosis 17Conjunctival follicles 17Conjunctival thickening associated with infiltrative

neoplasia 18Superficial conjunctival neoplasia 18Subconjunctival hemorrhage 18Conjunctival follicles 19Superficial conjunctival neoplasia 19Conjunctival neoplasia 19

5 Cornea 20Superficial corneal vascularization associated with

keratoconjunctivitis sicca 20Appearance of a dry cornea with concurrent anterior

uveitis 20Typical appearance of superficial corneal vessels 21Typical appearance of deep corneal vessels 21Typical appearance of corneal edema 21Corneal melanosis 22Typical melanin distribution associated with pigmentary

keratitis 22Typical appearance of corneal fibrosis with concurrent

corneal vascularization 22Corneal white cell infiltrate with concurrent corneal

vascularization and edema 23Corneal deposits associated with corneal dystrophy 23Corneal deposits associated with corneal dystrophy 23Corneal mineral deposits 24Typical changes associated with keratoconjunctivitis

sicca 24

viii Contents

Predominantly melanotic corneal changes associated with pannus 24

Predominantly fibrovascular corneal changes associated with pannus 25

Corneal changes associated with pannus mixture of melanosis and fibrovascular changes 25

Superficial corneal ulcer 25Indolent corneal ulcer with fluorescein stain applied 26Indolent corneal ulcer prior to fluorescein stain 26Indolent corneal ulcer after fluorescein stain 26Deep corneal ulcer 27Descemetocele after application of fluorescein stain 27Descemetocele after application of fluorescein stain

viewed with cobalt blue light 27Corneal perforation with iris prolapse 28Corneal perforation with iris prolapse and hyphema 28Corneal perforation with large iris prolapse 28Melting corneal ulcer 29Perforated melting corneal ulcer 29Dendritic corneal ulcers 29Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Corneal sequestrum light brown with minimal

keratitis 31Corneal sequestrum dark brown with moderate

keratoconjunctivitis 31Corneal sequestrum dark brown with significant

keratoconjunctivitis 31

6 Anterior uvea 32Iris-to-cornea persistent pupillary membranes 32Iris-to-iris persistent pupillary membranes 32Posterior synechiae 33Anterior chamber uveal cysts 33Anterior chamber uveal cysts 33Transillumination of posterior chamber uveal cysts 34Iris atrophy 34Iris atrophy 34Severe iris atrophy 35Focal iris hyperpigmentation 35Feline diffuse iris melanoma 35Feline diffuse iris melanoma 36Canine melanocytoma 36Canine melanocytoma 36Canine ciliary body adenoma 37Clinical signs of uveitis chemosis episcleral

congestion deep corneal vascularization and diffuse corneal edema 37

Aqueous flare 37Keratic precipitates 38Hypopyon with concurrent corneal ulceration 38Hyphema 38Rubeosis iridis 39Iris thickening 39

Posterior synechia 39Iris bombeacute 40

7 Lens 41Nuclear sclerosis 41Nuclear sclerosis 41Incipient cataract 42Incipient cataract 42Incomplete cataract 42Incomplete cataract 43Incomplete cataract 43Complete cataract 43Complete resorbing cataract 44Incomplete resorbing cataract 44Lens subluxation 44Lens subluxation 45Anterior lens luxation 45Posterior lens luxation 45

8 Posterior segment 46Normal canine fundus 46Normal canine fundus 46Normal feline fundus 47Subalbinotic atapetal canine fundus 47Subalbinotic feline fundus 47Tapetal hyperreflectivity and retinal vascular attenuation

in a cat 48Tapetal hyperreflectivity and retinal vascular attenuation

in a dog 48Focal retinal degenerationchorioretinal scar 48Focal retinal degenerationchorioretinal scar 49Tapetal hyporeflectivity due to hypertensive

retinopathy 49Tapetal hyporeflectivity 49Tapetal hyporeflectivity 50Fluid and white cell infiltrate in the nontapetal fundus

(chorioretinitis) 50Focal white cell infiltrate (chorioretinitis) and retinal

degeneration in the nontapetal fundus 50Multifocal retinal degeneration in the nontapetal

fundus 51Hemorrhage in the nontapetal fundus 51Hemorrhage in the tapetal fundus 51Serous retinal detachment and retinal hemorrhage due to

hypertensive retinopathy 52External view of serous retinal detachment 52Serous retinal detachment 52Rhegmatogenous retinal detachment 53Optic nerve atrophydegeneration - mild 53Optic nerve atrophydegeneration - severe 53Optic disc cupping in an atapetal fundus 54Optic disc cupping 54Optic neuritis 54Optic neuritis 55Asteroid hyalosis 55

Contents ix

Choroidal hypoplasia (collie eye anomaly) 55Posterior polar coloboma and choroidal hypoplasia

(collie eye anomaly) in a subalbinotic fundus 56

9 Glaucoma 57Typical appearance of acute glaucoma 57Haabrsquos striae 57

Section II Guide 59

10 Orbit 61Diseases of the orbit 62Brachycephalic ocular syndrome 62Hornerrsquos syndrome 63Orbital cellulitis and abscess 65Orbital neoplasia 67Proptosis 68Further reading 70References 70

11 Eyelids 71Diseases of the eyelid 72Distichiasis 72Ectopic cilia 73Trichiasis 73Eyelid agenesis 75Entropion 75Ectropion 77Eyelid neoplasia 78Chalazion 79Blepharitis 80Eyelid laceration 81Further reading 82References 82

12 The third eyelid nasolacrimal system and precorneal tear film 83Diseases of the third eyelid and lacrimal system 84Third eyelid gland prolapse (ldquocherry eyerdquo) 84Third eyelid neoplasia 85Nasolacrimal duct obstruction 87Tear film disordersmdashKCS 88Qualitative tear film abnormality 88References 90

13 Conjunctiva 91Diseases of conjunctiva 91Canine conjunctivitis 91Feline conjunctivitis 93Conjunctival neoplasia 95Further reading 96References 97

14 Cornea 98Corneal diseases 99Corneal dystrophy 99

Canine keratitis 100Keratoconjunctivitis sicca (KCS) 101Pigmentary keratitis 103Pannuschronic superficial keratitis 104Corneal ulceration 105Simple corneal ulceration 105Indolent corneal ulceration 106Deep and perforating corneal ulceration 108Melting corneal ulceration 110Feline keratitis nonulcerative and ulcerative 111Feline eosinophilic keratoconjunctivitis (EK) 112Corneal sequestrum 113Further reading 114References 114

15 Anterior uvea 116Anterior uveal diseases 116Persistent pupillary membranes (PPMs) 116Uveal cysts 117Iris atrophy 118Feline diffuse iris melanoma 118Canine anterior uveal melanocytic neoplasia 119Iridociliary neoplasia 120Anterior uveitis 121Further reading 124References 124

16 Lens 125Diseases of the lens 125Nuclear sclerosis 125Cataract 126Lens subluxation and luxation 128Further reading 129References 130

17 Posterior segment 131Diseases of the posterior segment 133Asteroid hyalosis 133Collie eye anomaly 133Progressive retinal atrophy (PRA) 134Sudden acquired retinal degeneration syndrome

(SARDS) 135Retinal degeneration (excluding PRA and SARDS) 136Chorioretinitis 137Retinal detachment 138Hypertensive retinopathy 140Optic neuritis 141Further reading 142References 142

18 Glaucoma 144Glaucoma 144Further reading 148References 148

Index 149

x

Preface

Small animal general practice is a high-paced profession that requires the veterinarian to arrive at a diagnosis and formulate diagnostic and therapeutic plans within a 15- to 20-minute appointment window As a general practitioner I often found myself in this position When I did I wished for a reference where I could find a photograph similar to what I observed in the patient along with enough information to implement a plan for treatment Such scenarios provided the idea for this book The Small Animal Ophthalmic Atlas and Guide is designed as a handy reference for the busy general practitioner The bookrsquos goals are to (i) provide an extensive collection of images that practitioners can use to obtain a diagnosis during an outpatient appointment and (ii) provide just enough information about each disease relevant diagnostic tests and treatment to allow for development of a medically sound management plan

The majority of ophthalmic conditions selected for inclusion in this book are those that present frequently in general practice A smaller number of less common conditions are also included because of their significant impact on vision andor overall health of the eye The purpose of this book is not to describe every known small animal ophthalmic disease nor is it intended

to be an exhaustive review of the diseases included in the book Because this is intended to be a quick reference each chapter includes only enough background information to facilitate discussion of each ocular disease most of the information is designed to support immediate management and only select procedures are detailed step-by-step (For example detailed directions for ocular surgeries should be sought from other texts) As a guide for those who wish to delve more deeply into specific ophthalmic conditions each chapter contains a list of suggestions for further reading

Of course no reference book can be a substitute for up-to-date education sound clinical judgment and the practitionerrsquos individual knowledge of a particular patient Readers of this book should always think critically about the cases presenting to them seek advice from and make referrals to veterinary oph-thalmologists when expert care is warranted and verify that new research or information from manufacturers has not eclipsed the information in this text My hope is that this book will make it easier for practitioners to handle ophthalmic cases in their daily practice

Christine C Lim

xi

List of abbreviations

CBC complete blood countCsA cyclosporine ACT computed tomographyDNA deoxyribonucleic acidDSH domestic shorthairERG electroretinogramFeLV feline leukemia virusFIP feline infectious peritonitisFHV-1 feline herpesvirusFIV feline immunodeficiency virusIOP intraocular pressureIV intravenous

KCS keratoconjunctivitis siccaLIU lens-induced uveitisMRI magnetic resonance imagingNSAID nonsteroidal anti-inflammatory drugPLR pupillary light reflexPO by mouthPPM persistent pupillary membranePRA progressive retinal atrophyRPE retinal pigmented epitheliumSARDS sudden acquired retinal degeneration

syndromeSTT Schirmer tear test

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

This edition first published 2015 copy 2015 by John Wiley amp Sons Inc

Editorial Offices1606 Golden Aspen Drive Suites 103 and 104 Ames Iowa 50014-8300 USAThe Atrium Southern Gate Chichester West Sussex PO19 8SQ UK9600 Garsington Road Oxford OX4 2DQ UK

For details of our global editorial offices for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at wwwwileycomwiley-blackwell

Authorization to photocopy items for internal or personal use or the internal or personal use of specific clients is granted by Blackwell Publishing provided that the base fee is paid directly to the Copyright Clearance Center 222 Rosewood Drive Danvers MA 01923 For those organizations that have been granted a photocopy license by CCC a separate system of payments has been arranged The fee codes for users of the Transactional Reporting Service are ISBN-13 978-1-1186-8976-92015

Designations used by companies to distinguish their products are often claimed as trademarks All brand names and product names used in this book are trade names service marks trademarks or registered trademarks of their respective owners The publisher is not associated with any product or vendor mentioned in this book

The contents of this work are intended to further general scientific research understanding and discussion only and are not intended and should not be relied upon as recommending or promoting a specific method diagnosis or treatment by health science practitioners for any particular patient The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties including without limitation any implied warranties of fitness for a particular purpose In view of ongoing research equipment modifications changes in governmental regulations and the constant flow of information relating to the use of medicines equipment and devices the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine equipment or device for among other things any changes in the instructions or indication of usage and for added warnings and precautions Readers should consult with a specialist where appropriate The fact that an organization or Website is referred to in this work as a citation andor a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make Further readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read No warranty may be created or extended by any promotional statements for this work Neither the publisher nor the author shall be liable for any damages arising herefrom

Library of Congress Cataloging-in-Publication Data applied for

A catalogue record for this book is available from the British Library

Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic books

Set in 9512pt Minion by SPi Publisher Services Pondicherry India

1 2015

To those who made this book possible my colleagues mentors students patients and of course my family

vii

Contents

Preface xList of abbreviations xiGlossary xii

Section I Atlas 1

1 Orbit 3Clinical signs associated with orbital neoplasia 3Clinical signs associated with orbital cellulitis 3Enophthalmos 4Brachycephalic ocular syndrome 4Ventromedial entropion associated with brachycephalic

ocular syndrome 4Clinical signs associated with Hornerrsquos syndrome 5Clinical signs associated with Hornerrsquos syndrome 5Appearance of Hornerrsquos syndrome following application of

sympathomimetic drugs 5Clinical signs associated with orbital neoplasia 6Clinical signs associated with proptosis 6

2 Eyelids 7Normal appearance of punctum 7Ectopic cilia 7Distichiae 8Distichiae 8Ectopic cilia and chalazion 8Lower eyelid entropion due to conformation 9Facial trichiasis 9Eyelid agenesis 9Appearance of entropion after temporary correction

using tacking sutures 10Lower eyelid ectropion 10Meibomian adenoma 10Meibomian adenoma 11Eyelid melanocytoma 11Chalazion 11Blepharitis 12Blepharitis 12Blepharitis 12

3 Third eyelid nasolacrimal system and precorneal tear film 13Pathologic changes to the third eyelid associated with

pannus 13

Scrolled third eyelid cartilage 13Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Superficial neoplasia of the third eyelid 14Neoplasia of the third eyelid gland 15Positive Jones test ndash appearance of fluorescein

in mouth 15Positive Jones test ndash appearance of fluorescein

at nostril 15

4 Conjunctiva 16Normal appearance of the conjunctiva 16Conjunctival hyperemia 16Chemosis and conjunctival hyperemia 17Chemosis 17Conjunctival follicles 17Conjunctival thickening associated with infiltrative

neoplasia 18Superficial conjunctival neoplasia 18Subconjunctival hemorrhage 18Conjunctival follicles 19Superficial conjunctival neoplasia 19Conjunctival neoplasia 19

5 Cornea 20Superficial corneal vascularization associated with

keratoconjunctivitis sicca 20Appearance of a dry cornea with concurrent anterior

uveitis 20Typical appearance of superficial corneal vessels 21Typical appearance of deep corneal vessels 21Typical appearance of corneal edema 21Corneal melanosis 22Typical melanin distribution associated with pigmentary

keratitis 22Typical appearance of corneal fibrosis with concurrent

corneal vascularization 22Corneal white cell infiltrate with concurrent corneal

vascularization and edema 23Corneal deposits associated with corneal dystrophy 23Corneal deposits associated with corneal dystrophy 23Corneal mineral deposits 24Typical changes associated with keratoconjunctivitis

sicca 24

viii Contents

Predominantly melanotic corneal changes associated with pannus 24

Predominantly fibrovascular corneal changes associated with pannus 25

Corneal changes associated with pannus mixture of melanosis and fibrovascular changes 25

Superficial corneal ulcer 25Indolent corneal ulcer with fluorescein stain applied 26Indolent corneal ulcer prior to fluorescein stain 26Indolent corneal ulcer after fluorescein stain 26Deep corneal ulcer 27Descemetocele after application of fluorescein stain 27Descemetocele after application of fluorescein stain

viewed with cobalt blue light 27Corneal perforation with iris prolapse 28Corneal perforation with iris prolapse and hyphema 28Corneal perforation with large iris prolapse 28Melting corneal ulcer 29Perforated melting corneal ulcer 29Dendritic corneal ulcers 29Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Corneal sequestrum light brown with minimal

keratitis 31Corneal sequestrum dark brown with moderate

keratoconjunctivitis 31Corneal sequestrum dark brown with significant

keratoconjunctivitis 31

6 Anterior uvea 32Iris-to-cornea persistent pupillary membranes 32Iris-to-iris persistent pupillary membranes 32Posterior synechiae 33Anterior chamber uveal cysts 33Anterior chamber uveal cysts 33Transillumination of posterior chamber uveal cysts 34Iris atrophy 34Iris atrophy 34Severe iris atrophy 35Focal iris hyperpigmentation 35Feline diffuse iris melanoma 35Feline diffuse iris melanoma 36Canine melanocytoma 36Canine melanocytoma 36Canine ciliary body adenoma 37Clinical signs of uveitis chemosis episcleral

congestion deep corneal vascularization and diffuse corneal edema 37

Aqueous flare 37Keratic precipitates 38Hypopyon with concurrent corneal ulceration 38Hyphema 38Rubeosis iridis 39Iris thickening 39

Posterior synechia 39Iris bombeacute 40

7 Lens 41Nuclear sclerosis 41Nuclear sclerosis 41Incipient cataract 42Incipient cataract 42Incomplete cataract 42Incomplete cataract 43Incomplete cataract 43Complete cataract 43Complete resorbing cataract 44Incomplete resorbing cataract 44Lens subluxation 44Lens subluxation 45Anterior lens luxation 45Posterior lens luxation 45

8 Posterior segment 46Normal canine fundus 46Normal canine fundus 46Normal feline fundus 47Subalbinotic atapetal canine fundus 47Subalbinotic feline fundus 47Tapetal hyperreflectivity and retinal vascular attenuation

in a cat 48Tapetal hyperreflectivity and retinal vascular attenuation

in a dog 48Focal retinal degenerationchorioretinal scar 48Focal retinal degenerationchorioretinal scar 49Tapetal hyporeflectivity due to hypertensive

retinopathy 49Tapetal hyporeflectivity 49Tapetal hyporeflectivity 50Fluid and white cell infiltrate in the nontapetal fundus

(chorioretinitis) 50Focal white cell infiltrate (chorioretinitis) and retinal

degeneration in the nontapetal fundus 50Multifocal retinal degeneration in the nontapetal

fundus 51Hemorrhage in the nontapetal fundus 51Hemorrhage in the tapetal fundus 51Serous retinal detachment and retinal hemorrhage due to

hypertensive retinopathy 52External view of serous retinal detachment 52Serous retinal detachment 52Rhegmatogenous retinal detachment 53Optic nerve atrophydegeneration - mild 53Optic nerve atrophydegeneration - severe 53Optic disc cupping in an atapetal fundus 54Optic disc cupping 54Optic neuritis 54Optic neuritis 55Asteroid hyalosis 55

Contents ix

Choroidal hypoplasia (collie eye anomaly) 55Posterior polar coloboma and choroidal hypoplasia

(collie eye anomaly) in a subalbinotic fundus 56

9 Glaucoma 57Typical appearance of acute glaucoma 57Haabrsquos striae 57

Section II Guide 59

10 Orbit 61Diseases of the orbit 62Brachycephalic ocular syndrome 62Hornerrsquos syndrome 63Orbital cellulitis and abscess 65Orbital neoplasia 67Proptosis 68Further reading 70References 70

11 Eyelids 71Diseases of the eyelid 72Distichiasis 72Ectopic cilia 73Trichiasis 73Eyelid agenesis 75Entropion 75Ectropion 77Eyelid neoplasia 78Chalazion 79Blepharitis 80Eyelid laceration 81Further reading 82References 82

12 The third eyelid nasolacrimal system and precorneal tear film 83Diseases of the third eyelid and lacrimal system 84Third eyelid gland prolapse (ldquocherry eyerdquo) 84Third eyelid neoplasia 85Nasolacrimal duct obstruction 87Tear film disordersmdashKCS 88Qualitative tear film abnormality 88References 90

13 Conjunctiva 91Diseases of conjunctiva 91Canine conjunctivitis 91Feline conjunctivitis 93Conjunctival neoplasia 95Further reading 96References 97

14 Cornea 98Corneal diseases 99Corneal dystrophy 99

Canine keratitis 100Keratoconjunctivitis sicca (KCS) 101Pigmentary keratitis 103Pannuschronic superficial keratitis 104Corneal ulceration 105Simple corneal ulceration 105Indolent corneal ulceration 106Deep and perforating corneal ulceration 108Melting corneal ulceration 110Feline keratitis nonulcerative and ulcerative 111Feline eosinophilic keratoconjunctivitis (EK) 112Corneal sequestrum 113Further reading 114References 114

15 Anterior uvea 116Anterior uveal diseases 116Persistent pupillary membranes (PPMs) 116Uveal cysts 117Iris atrophy 118Feline diffuse iris melanoma 118Canine anterior uveal melanocytic neoplasia 119Iridociliary neoplasia 120Anterior uveitis 121Further reading 124References 124

16 Lens 125Diseases of the lens 125Nuclear sclerosis 125Cataract 126Lens subluxation and luxation 128Further reading 129References 130

17 Posterior segment 131Diseases of the posterior segment 133Asteroid hyalosis 133Collie eye anomaly 133Progressive retinal atrophy (PRA) 134Sudden acquired retinal degeneration syndrome

(SARDS) 135Retinal degeneration (excluding PRA and SARDS) 136Chorioretinitis 137Retinal detachment 138Hypertensive retinopathy 140Optic neuritis 141Further reading 142References 142

18 Glaucoma 144Glaucoma 144Further reading 148References 148

Index 149

x

Preface

Small animal general practice is a high-paced profession that requires the veterinarian to arrive at a diagnosis and formulate diagnostic and therapeutic plans within a 15- to 20-minute appointment window As a general practitioner I often found myself in this position When I did I wished for a reference where I could find a photograph similar to what I observed in the patient along with enough information to implement a plan for treatment Such scenarios provided the idea for this book The Small Animal Ophthalmic Atlas and Guide is designed as a handy reference for the busy general practitioner The bookrsquos goals are to (i) provide an extensive collection of images that practitioners can use to obtain a diagnosis during an outpatient appointment and (ii) provide just enough information about each disease relevant diagnostic tests and treatment to allow for development of a medically sound management plan

The majority of ophthalmic conditions selected for inclusion in this book are those that present frequently in general practice A smaller number of less common conditions are also included because of their significant impact on vision andor overall health of the eye The purpose of this book is not to describe every known small animal ophthalmic disease nor is it intended

to be an exhaustive review of the diseases included in the book Because this is intended to be a quick reference each chapter includes only enough background information to facilitate discussion of each ocular disease most of the information is designed to support immediate management and only select procedures are detailed step-by-step (For example detailed directions for ocular surgeries should be sought from other texts) As a guide for those who wish to delve more deeply into specific ophthalmic conditions each chapter contains a list of suggestions for further reading

Of course no reference book can be a substitute for up-to-date education sound clinical judgment and the practitionerrsquos individual knowledge of a particular patient Readers of this book should always think critically about the cases presenting to them seek advice from and make referrals to veterinary oph-thalmologists when expert care is warranted and verify that new research or information from manufacturers has not eclipsed the information in this text My hope is that this book will make it easier for practitioners to handle ophthalmic cases in their daily practice

Christine C Lim

xi

List of abbreviations

CBC complete blood countCsA cyclosporine ACT computed tomographyDNA deoxyribonucleic acidDSH domestic shorthairERG electroretinogramFeLV feline leukemia virusFIP feline infectious peritonitisFHV-1 feline herpesvirusFIV feline immunodeficiency virusIOP intraocular pressureIV intravenous

KCS keratoconjunctivitis siccaLIU lens-induced uveitisMRI magnetic resonance imagingNSAID nonsteroidal anti-inflammatory drugPLR pupillary light reflexPO by mouthPPM persistent pupillary membranePRA progressive retinal atrophyRPE retinal pigmented epitheliumSARDS sudden acquired retinal degeneration

syndromeSTT Schirmer tear test

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

To those who made this book possible my colleagues mentors students patients and of course my family

vii

Contents

Preface xList of abbreviations xiGlossary xii

Section I Atlas 1

1 Orbit 3Clinical signs associated with orbital neoplasia 3Clinical signs associated with orbital cellulitis 3Enophthalmos 4Brachycephalic ocular syndrome 4Ventromedial entropion associated with brachycephalic

ocular syndrome 4Clinical signs associated with Hornerrsquos syndrome 5Clinical signs associated with Hornerrsquos syndrome 5Appearance of Hornerrsquos syndrome following application of

sympathomimetic drugs 5Clinical signs associated with orbital neoplasia 6Clinical signs associated with proptosis 6

2 Eyelids 7Normal appearance of punctum 7Ectopic cilia 7Distichiae 8Distichiae 8Ectopic cilia and chalazion 8Lower eyelid entropion due to conformation 9Facial trichiasis 9Eyelid agenesis 9Appearance of entropion after temporary correction

using tacking sutures 10Lower eyelid ectropion 10Meibomian adenoma 10Meibomian adenoma 11Eyelid melanocytoma 11Chalazion 11Blepharitis 12Blepharitis 12Blepharitis 12

3 Third eyelid nasolacrimal system and precorneal tear film 13Pathologic changes to the third eyelid associated with

pannus 13

Scrolled third eyelid cartilage 13Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Superficial neoplasia of the third eyelid 14Neoplasia of the third eyelid gland 15Positive Jones test ndash appearance of fluorescein

in mouth 15Positive Jones test ndash appearance of fluorescein

at nostril 15

4 Conjunctiva 16Normal appearance of the conjunctiva 16Conjunctival hyperemia 16Chemosis and conjunctival hyperemia 17Chemosis 17Conjunctival follicles 17Conjunctival thickening associated with infiltrative

neoplasia 18Superficial conjunctival neoplasia 18Subconjunctival hemorrhage 18Conjunctival follicles 19Superficial conjunctival neoplasia 19Conjunctival neoplasia 19

5 Cornea 20Superficial corneal vascularization associated with

keratoconjunctivitis sicca 20Appearance of a dry cornea with concurrent anterior

uveitis 20Typical appearance of superficial corneal vessels 21Typical appearance of deep corneal vessels 21Typical appearance of corneal edema 21Corneal melanosis 22Typical melanin distribution associated with pigmentary

keratitis 22Typical appearance of corneal fibrosis with concurrent

corneal vascularization 22Corneal white cell infiltrate with concurrent corneal

vascularization and edema 23Corneal deposits associated with corneal dystrophy 23Corneal deposits associated with corneal dystrophy 23Corneal mineral deposits 24Typical changes associated with keratoconjunctivitis

sicca 24

viii Contents

Predominantly melanotic corneal changes associated with pannus 24

Predominantly fibrovascular corneal changes associated with pannus 25

Corneal changes associated with pannus mixture of melanosis and fibrovascular changes 25

Superficial corneal ulcer 25Indolent corneal ulcer with fluorescein stain applied 26Indolent corneal ulcer prior to fluorescein stain 26Indolent corneal ulcer after fluorescein stain 26Deep corneal ulcer 27Descemetocele after application of fluorescein stain 27Descemetocele after application of fluorescein stain

viewed with cobalt blue light 27Corneal perforation with iris prolapse 28Corneal perforation with iris prolapse and hyphema 28Corneal perforation with large iris prolapse 28Melting corneal ulcer 29Perforated melting corneal ulcer 29Dendritic corneal ulcers 29Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Corneal sequestrum light brown with minimal

keratitis 31Corneal sequestrum dark brown with moderate

keratoconjunctivitis 31Corneal sequestrum dark brown with significant

keratoconjunctivitis 31

6 Anterior uvea 32Iris-to-cornea persistent pupillary membranes 32Iris-to-iris persistent pupillary membranes 32Posterior synechiae 33Anterior chamber uveal cysts 33Anterior chamber uveal cysts 33Transillumination of posterior chamber uveal cysts 34Iris atrophy 34Iris atrophy 34Severe iris atrophy 35Focal iris hyperpigmentation 35Feline diffuse iris melanoma 35Feline diffuse iris melanoma 36Canine melanocytoma 36Canine melanocytoma 36Canine ciliary body adenoma 37Clinical signs of uveitis chemosis episcleral

congestion deep corneal vascularization and diffuse corneal edema 37

Aqueous flare 37Keratic precipitates 38Hypopyon with concurrent corneal ulceration 38Hyphema 38Rubeosis iridis 39Iris thickening 39

Posterior synechia 39Iris bombeacute 40

7 Lens 41Nuclear sclerosis 41Nuclear sclerosis 41Incipient cataract 42Incipient cataract 42Incomplete cataract 42Incomplete cataract 43Incomplete cataract 43Complete cataract 43Complete resorbing cataract 44Incomplete resorbing cataract 44Lens subluxation 44Lens subluxation 45Anterior lens luxation 45Posterior lens luxation 45

8 Posterior segment 46Normal canine fundus 46Normal canine fundus 46Normal feline fundus 47Subalbinotic atapetal canine fundus 47Subalbinotic feline fundus 47Tapetal hyperreflectivity and retinal vascular attenuation

in a cat 48Tapetal hyperreflectivity and retinal vascular attenuation

in a dog 48Focal retinal degenerationchorioretinal scar 48Focal retinal degenerationchorioretinal scar 49Tapetal hyporeflectivity due to hypertensive

retinopathy 49Tapetal hyporeflectivity 49Tapetal hyporeflectivity 50Fluid and white cell infiltrate in the nontapetal fundus

(chorioretinitis) 50Focal white cell infiltrate (chorioretinitis) and retinal

degeneration in the nontapetal fundus 50Multifocal retinal degeneration in the nontapetal

fundus 51Hemorrhage in the nontapetal fundus 51Hemorrhage in the tapetal fundus 51Serous retinal detachment and retinal hemorrhage due to

hypertensive retinopathy 52External view of serous retinal detachment 52Serous retinal detachment 52Rhegmatogenous retinal detachment 53Optic nerve atrophydegeneration - mild 53Optic nerve atrophydegeneration - severe 53Optic disc cupping in an atapetal fundus 54Optic disc cupping 54Optic neuritis 54Optic neuritis 55Asteroid hyalosis 55

Contents ix

Choroidal hypoplasia (collie eye anomaly) 55Posterior polar coloboma and choroidal hypoplasia

(collie eye anomaly) in a subalbinotic fundus 56

9 Glaucoma 57Typical appearance of acute glaucoma 57Haabrsquos striae 57

Section II Guide 59

10 Orbit 61Diseases of the orbit 62Brachycephalic ocular syndrome 62Hornerrsquos syndrome 63Orbital cellulitis and abscess 65Orbital neoplasia 67Proptosis 68Further reading 70References 70

11 Eyelids 71Diseases of the eyelid 72Distichiasis 72Ectopic cilia 73Trichiasis 73Eyelid agenesis 75Entropion 75Ectropion 77Eyelid neoplasia 78Chalazion 79Blepharitis 80Eyelid laceration 81Further reading 82References 82

12 The third eyelid nasolacrimal system and precorneal tear film 83Diseases of the third eyelid and lacrimal system 84Third eyelid gland prolapse (ldquocherry eyerdquo) 84Third eyelid neoplasia 85Nasolacrimal duct obstruction 87Tear film disordersmdashKCS 88Qualitative tear film abnormality 88References 90

13 Conjunctiva 91Diseases of conjunctiva 91Canine conjunctivitis 91Feline conjunctivitis 93Conjunctival neoplasia 95Further reading 96References 97

14 Cornea 98Corneal diseases 99Corneal dystrophy 99

Canine keratitis 100Keratoconjunctivitis sicca (KCS) 101Pigmentary keratitis 103Pannuschronic superficial keratitis 104Corneal ulceration 105Simple corneal ulceration 105Indolent corneal ulceration 106Deep and perforating corneal ulceration 108Melting corneal ulceration 110Feline keratitis nonulcerative and ulcerative 111Feline eosinophilic keratoconjunctivitis (EK) 112Corneal sequestrum 113Further reading 114References 114

15 Anterior uvea 116Anterior uveal diseases 116Persistent pupillary membranes (PPMs) 116Uveal cysts 117Iris atrophy 118Feline diffuse iris melanoma 118Canine anterior uveal melanocytic neoplasia 119Iridociliary neoplasia 120Anterior uveitis 121Further reading 124References 124

16 Lens 125Diseases of the lens 125Nuclear sclerosis 125Cataract 126Lens subluxation and luxation 128Further reading 129References 130

17 Posterior segment 131Diseases of the posterior segment 133Asteroid hyalosis 133Collie eye anomaly 133Progressive retinal atrophy (PRA) 134Sudden acquired retinal degeneration syndrome

(SARDS) 135Retinal degeneration (excluding PRA and SARDS) 136Chorioretinitis 137Retinal detachment 138Hypertensive retinopathy 140Optic neuritis 141Further reading 142References 142

18 Glaucoma 144Glaucoma 144Further reading 148References 148

Index 149

x

Preface

Small animal general practice is a high-paced profession that requires the veterinarian to arrive at a diagnosis and formulate diagnostic and therapeutic plans within a 15- to 20-minute appointment window As a general practitioner I often found myself in this position When I did I wished for a reference where I could find a photograph similar to what I observed in the patient along with enough information to implement a plan for treatment Such scenarios provided the idea for this book The Small Animal Ophthalmic Atlas and Guide is designed as a handy reference for the busy general practitioner The bookrsquos goals are to (i) provide an extensive collection of images that practitioners can use to obtain a diagnosis during an outpatient appointment and (ii) provide just enough information about each disease relevant diagnostic tests and treatment to allow for development of a medically sound management plan

The majority of ophthalmic conditions selected for inclusion in this book are those that present frequently in general practice A smaller number of less common conditions are also included because of their significant impact on vision andor overall health of the eye The purpose of this book is not to describe every known small animal ophthalmic disease nor is it intended

to be an exhaustive review of the diseases included in the book Because this is intended to be a quick reference each chapter includes only enough background information to facilitate discussion of each ocular disease most of the information is designed to support immediate management and only select procedures are detailed step-by-step (For example detailed directions for ocular surgeries should be sought from other texts) As a guide for those who wish to delve more deeply into specific ophthalmic conditions each chapter contains a list of suggestions for further reading

Of course no reference book can be a substitute for up-to-date education sound clinical judgment and the practitionerrsquos individual knowledge of a particular patient Readers of this book should always think critically about the cases presenting to them seek advice from and make referrals to veterinary oph-thalmologists when expert care is warranted and verify that new research or information from manufacturers has not eclipsed the information in this text My hope is that this book will make it easier for practitioners to handle ophthalmic cases in their daily practice

Christine C Lim

xi

List of abbreviations

CBC complete blood countCsA cyclosporine ACT computed tomographyDNA deoxyribonucleic acidDSH domestic shorthairERG electroretinogramFeLV feline leukemia virusFIP feline infectious peritonitisFHV-1 feline herpesvirusFIV feline immunodeficiency virusIOP intraocular pressureIV intravenous

KCS keratoconjunctivitis siccaLIU lens-induced uveitisMRI magnetic resonance imagingNSAID nonsteroidal anti-inflammatory drugPLR pupillary light reflexPO by mouthPPM persistent pupillary membranePRA progressive retinal atrophyRPE retinal pigmented epitheliumSARDS sudden acquired retinal degeneration

syndromeSTT Schirmer tear test

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

vii

Contents

Preface xList of abbreviations xiGlossary xii

Section I Atlas 1

1 Orbit 3Clinical signs associated with orbital neoplasia 3Clinical signs associated with orbital cellulitis 3Enophthalmos 4Brachycephalic ocular syndrome 4Ventromedial entropion associated with brachycephalic

ocular syndrome 4Clinical signs associated with Hornerrsquos syndrome 5Clinical signs associated with Hornerrsquos syndrome 5Appearance of Hornerrsquos syndrome following application of

sympathomimetic drugs 5Clinical signs associated with orbital neoplasia 6Clinical signs associated with proptosis 6

2 Eyelids 7Normal appearance of punctum 7Ectopic cilia 7Distichiae 8Distichiae 8Ectopic cilia and chalazion 8Lower eyelid entropion due to conformation 9Facial trichiasis 9Eyelid agenesis 9Appearance of entropion after temporary correction

using tacking sutures 10Lower eyelid ectropion 10Meibomian adenoma 10Meibomian adenoma 11Eyelid melanocytoma 11Chalazion 11Blepharitis 12Blepharitis 12Blepharitis 12

3 Third eyelid nasolacrimal system and precorneal tear film 13Pathologic changes to the third eyelid associated with

pannus 13

Scrolled third eyelid cartilage 13Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Prolapsed third eyelid gland (ldquocherry eyerdquo) 14Superficial neoplasia of the third eyelid 14Neoplasia of the third eyelid gland 15Positive Jones test ndash appearance of fluorescein

in mouth 15Positive Jones test ndash appearance of fluorescein

at nostril 15

4 Conjunctiva 16Normal appearance of the conjunctiva 16Conjunctival hyperemia 16Chemosis and conjunctival hyperemia 17Chemosis 17Conjunctival follicles 17Conjunctival thickening associated with infiltrative

neoplasia 18Superficial conjunctival neoplasia 18Subconjunctival hemorrhage 18Conjunctival follicles 19Superficial conjunctival neoplasia 19Conjunctival neoplasia 19

5 Cornea 20Superficial corneal vascularization associated with

keratoconjunctivitis sicca 20Appearance of a dry cornea with concurrent anterior

uveitis 20Typical appearance of superficial corneal vessels 21Typical appearance of deep corneal vessels 21Typical appearance of corneal edema 21Corneal melanosis 22Typical melanin distribution associated with pigmentary

keratitis 22Typical appearance of corneal fibrosis with concurrent

corneal vascularization 22Corneal white cell infiltrate with concurrent corneal

vascularization and edema 23Corneal deposits associated with corneal dystrophy 23Corneal deposits associated with corneal dystrophy 23Corneal mineral deposits 24Typical changes associated with keratoconjunctivitis

sicca 24

viii Contents

Predominantly melanotic corneal changes associated with pannus 24

Predominantly fibrovascular corneal changes associated with pannus 25

Corneal changes associated with pannus mixture of melanosis and fibrovascular changes 25

Superficial corneal ulcer 25Indolent corneal ulcer with fluorescein stain applied 26Indolent corneal ulcer prior to fluorescein stain 26Indolent corneal ulcer after fluorescein stain 26Deep corneal ulcer 27Descemetocele after application of fluorescein stain 27Descemetocele after application of fluorescein stain

viewed with cobalt blue light 27Corneal perforation with iris prolapse 28Corneal perforation with iris prolapse and hyphema 28Corneal perforation with large iris prolapse 28Melting corneal ulcer 29Perforated melting corneal ulcer 29Dendritic corneal ulcers 29Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Corneal sequestrum light brown with minimal

keratitis 31Corneal sequestrum dark brown with moderate

keratoconjunctivitis 31Corneal sequestrum dark brown with significant

keratoconjunctivitis 31

6 Anterior uvea 32Iris-to-cornea persistent pupillary membranes 32Iris-to-iris persistent pupillary membranes 32Posterior synechiae 33Anterior chamber uveal cysts 33Anterior chamber uveal cysts 33Transillumination of posterior chamber uveal cysts 34Iris atrophy 34Iris atrophy 34Severe iris atrophy 35Focal iris hyperpigmentation 35Feline diffuse iris melanoma 35Feline diffuse iris melanoma 36Canine melanocytoma 36Canine melanocytoma 36Canine ciliary body adenoma 37Clinical signs of uveitis chemosis episcleral

congestion deep corneal vascularization and diffuse corneal edema 37

Aqueous flare 37Keratic precipitates 38Hypopyon with concurrent corneal ulceration 38Hyphema 38Rubeosis iridis 39Iris thickening 39

Posterior synechia 39Iris bombeacute 40

7 Lens 41Nuclear sclerosis 41Nuclear sclerosis 41Incipient cataract 42Incipient cataract 42Incomplete cataract 42Incomplete cataract 43Incomplete cataract 43Complete cataract 43Complete resorbing cataract 44Incomplete resorbing cataract 44Lens subluxation 44Lens subluxation 45Anterior lens luxation 45Posterior lens luxation 45

8 Posterior segment 46Normal canine fundus 46Normal canine fundus 46Normal feline fundus 47Subalbinotic atapetal canine fundus 47Subalbinotic feline fundus 47Tapetal hyperreflectivity and retinal vascular attenuation

in a cat 48Tapetal hyperreflectivity and retinal vascular attenuation

in a dog 48Focal retinal degenerationchorioretinal scar 48Focal retinal degenerationchorioretinal scar 49Tapetal hyporeflectivity due to hypertensive

retinopathy 49Tapetal hyporeflectivity 49Tapetal hyporeflectivity 50Fluid and white cell infiltrate in the nontapetal fundus

(chorioretinitis) 50Focal white cell infiltrate (chorioretinitis) and retinal

degeneration in the nontapetal fundus 50Multifocal retinal degeneration in the nontapetal

fundus 51Hemorrhage in the nontapetal fundus 51Hemorrhage in the tapetal fundus 51Serous retinal detachment and retinal hemorrhage due to

hypertensive retinopathy 52External view of serous retinal detachment 52Serous retinal detachment 52Rhegmatogenous retinal detachment 53Optic nerve atrophydegeneration - mild 53Optic nerve atrophydegeneration - severe 53Optic disc cupping in an atapetal fundus 54Optic disc cupping 54Optic neuritis 54Optic neuritis 55Asteroid hyalosis 55

Contents ix

Choroidal hypoplasia (collie eye anomaly) 55Posterior polar coloboma and choroidal hypoplasia

(collie eye anomaly) in a subalbinotic fundus 56

9 Glaucoma 57Typical appearance of acute glaucoma 57Haabrsquos striae 57

Section II Guide 59

10 Orbit 61Diseases of the orbit 62Brachycephalic ocular syndrome 62Hornerrsquos syndrome 63Orbital cellulitis and abscess 65Orbital neoplasia 67Proptosis 68Further reading 70References 70

11 Eyelids 71Diseases of the eyelid 72Distichiasis 72Ectopic cilia 73Trichiasis 73Eyelid agenesis 75Entropion 75Ectropion 77Eyelid neoplasia 78Chalazion 79Blepharitis 80Eyelid laceration 81Further reading 82References 82

12 The third eyelid nasolacrimal system and precorneal tear film 83Diseases of the third eyelid and lacrimal system 84Third eyelid gland prolapse (ldquocherry eyerdquo) 84Third eyelid neoplasia 85Nasolacrimal duct obstruction 87Tear film disordersmdashKCS 88Qualitative tear film abnormality 88References 90

13 Conjunctiva 91Diseases of conjunctiva 91Canine conjunctivitis 91Feline conjunctivitis 93Conjunctival neoplasia 95Further reading 96References 97

14 Cornea 98Corneal diseases 99Corneal dystrophy 99

Canine keratitis 100Keratoconjunctivitis sicca (KCS) 101Pigmentary keratitis 103Pannuschronic superficial keratitis 104Corneal ulceration 105Simple corneal ulceration 105Indolent corneal ulceration 106Deep and perforating corneal ulceration 108Melting corneal ulceration 110Feline keratitis nonulcerative and ulcerative 111Feline eosinophilic keratoconjunctivitis (EK) 112Corneal sequestrum 113Further reading 114References 114

15 Anterior uvea 116Anterior uveal diseases 116Persistent pupillary membranes (PPMs) 116Uveal cysts 117Iris atrophy 118Feline diffuse iris melanoma 118Canine anterior uveal melanocytic neoplasia 119Iridociliary neoplasia 120Anterior uveitis 121Further reading 124References 124

16 Lens 125Diseases of the lens 125Nuclear sclerosis 125Cataract 126Lens subluxation and luxation 128Further reading 129References 130

17 Posterior segment 131Diseases of the posterior segment 133Asteroid hyalosis 133Collie eye anomaly 133Progressive retinal atrophy (PRA) 134Sudden acquired retinal degeneration syndrome

(SARDS) 135Retinal degeneration (excluding PRA and SARDS) 136Chorioretinitis 137Retinal detachment 138Hypertensive retinopathy 140Optic neuritis 141Further reading 142References 142

18 Glaucoma 144Glaucoma 144Further reading 148References 148

Index 149

x

Preface

Small animal general practice is a high-paced profession that requires the veterinarian to arrive at a diagnosis and formulate diagnostic and therapeutic plans within a 15- to 20-minute appointment window As a general practitioner I often found myself in this position When I did I wished for a reference where I could find a photograph similar to what I observed in the patient along with enough information to implement a plan for treatment Such scenarios provided the idea for this book The Small Animal Ophthalmic Atlas and Guide is designed as a handy reference for the busy general practitioner The bookrsquos goals are to (i) provide an extensive collection of images that practitioners can use to obtain a diagnosis during an outpatient appointment and (ii) provide just enough information about each disease relevant diagnostic tests and treatment to allow for development of a medically sound management plan

The majority of ophthalmic conditions selected for inclusion in this book are those that present frequently in general practice A smaller number of less common conditions are also included because of their significant impact on vision andor overall health of the eye The purpose of this book is not to describe every known small animal ophthalmic disease nor is it intended

to be an exhaustive review of the diseases included in the book Because this is intended to be a quick reference each chapter includes only enough background information to facilitate discussion of each ocular disease most of the information is designed to support immediate management and only select procedures are detailed step-by-step (For example detailed directions for ocular surgeries should be sought from other texts) As a guide for those who wish to delve more deeply into specific ophthalmic conditions each chapter contains a list of suggestions for further reading

Of course no reference book can be a substitute for up-to-date education sound clinical judgment and the practitionerrsquos individual knowledge of a particular patient Readers of this book should always think critically about the cases presenting to them seek advice from and make referrals to veterinary oph-thalmologists when expert care is warranted and verify that new research or information from manufacturers has not eclipsed the information in this text My hope is that this book will make it easier for practitioners to handle ophthalmic cases in their daily practice

Christine C Lim

xi

List of abbreviations

CBC complete blood countCsA cyclosporine ACT computed tomographyDNA deoxyribonucleic acidDSH domestic shorthairERG electroretinogramFeLV feline leukemia virusFIP feline infectious peritonitisFHV-1 feline herpesvirusFIV feline immunodeficiency virusIOP intraocular pressureIV intravenous

KCS keratoconjunctivitis siccaLIU lens-induced uveitisMRI magnetic resonance imagingNSAID nonsteroidal anti-inflammatory drugPLR pupillary light reflexPO by mouthPPM persistent pupillary membranePRA progressive retinal atrophyRPE retinal pigmented epitheliumSARDS sudden acquired retinal degeneration

syndromeSTT Schirmer tear test

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

viii Contents

Predominantly melanotic corneal changes associated with pannus 24

Predominantly fibrovascular corneal changes associated with pannus 25

Corneal changes associated with pannus mixture of melanosis and fibrovascular changes 25

Superficial corneal ulcer 25Indolent corneal ulcer with fluorescein stain applied 26Indolent corneal ulcer prior to fluorescein stain 26Indolent corneal ulcer after fluorescein stain 26Deep corneal ulcer 27Descemetocele after application of fluorescein stain 27Descemetocele after application of fluorescein stain

viewed with cobalt blue light 27Corneal perforation with iris prolapse 28Corneal perforation with iris prolapse and hyphema 28Corneal perforation with large iris prolapse 28Melting corneal ulcer 29Perforated melting corneal ulcer 29Dendritic corneal ulcers 29Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Eosinophilic keratoconjunctivitis 30Corneal sequestrum light brown with minimal

keratitis 31Corneal sequestrum dark brown with moderate

keratoconjunctivitis 31Corneal sequestrum dark brown with significant

keratoconjunctivitis 31

6 Anterior uvea 32Iris-to-cornea persistent pupillary membranes 32Iris-to-iris persistent pupillary membranes 32Posterior synechiae 33Anterior chamber uveal cysts 33Anterior chamber uveal cysts 33Transillumination of posterior chamber uveal cysts 34Iris atrophy 34Iris atrophy 34Severe iris atrophy 35Focal iris hyperpigmentation 35Feline diffuse iris melanoma 35Feline diffuse iris melanoma 36Canine melanocytoma 36Canine melanocytoma 36Canine ciliary body adenoma 37Clinical signs of uveitis chemosis episcleral

congestion deep corneal vascularization and diffuse corneal edema 37

Aqueous flare 37Keratic precipitates 38Hypopyon with concurrent corneal ulceration 38Hyphema 38Rubeosis iridis 39Iris thickening 39

Posterior synechia 39Iris bombeacute 40

7 Lens 41Nuclear sclerosis 41Nuclear sclerosis 41Incipient cataract 42Incipient cataract 42Incomplete cataract 42Incomplete cataract 43Incomplete cataract 43Complete cataract 43Complete resorbing cataract 44Incomplete resorbing cataract 44Lens subluxation 44Lens subluxation 45Anterior lens luxation 45Posterior lens luxation 45

8 Posterior segment 46Normal canine fundus 46Normal canine fundus 46Normal feline fundus 47Subalbinotic atapetal canine fundus 47Subalbinotic feline fundus 47Tapetal hyperreflectivity and retinal vascular attenuation

in a cat 48Tapetal hyperreflectivity and retinal vascular attenuation

in a dog 48Focal retinal degenerationchorioretinal scar 48Focal retinal degenerationchorioretinal scar 49Tapetal hyporeflectivity due to hypertensive

retinopathy 49Tapetal hyporeflectivity 49Tapetal hyporeflectivity 50Fluid and white cell infiltrate in the nontapetal fundus

(chorioretinitis) 50Focal white cell infiltrate (chorioretinitis) and retinal

degeneration in the nontapetal fundus 50Multifocal retinal degeneration in the nontapetal

fundus 51Hemorrhage in the nontapetal fundus 51Hemorrhage in the tapetal fundus 51Serous retinal detachment and retinal hemorrhage due to

hypertensive retinopathy 52External view of serous retinal detachment 52Serous retinal detachment 52Rhegmatogenous retinal detachment 53Optic nerve atrophydegeneration - mild 53Optic nerve atrophydegeneration - severe 53Optic disc cupping in an atapetal fundus 54Optic disc cupping 54Optic neuritis 54Optic neuritis 55Asteroid hyalosis 55

Contents ix

Choroidal hypoplasia (collie eye anomaly) 55Posterior polar coloboma and choroidal hypoplasia

(collie eye anomaly) in a subalbinotic fundus 56

9 Glaucoma 57Typical appearance of acute glaucoma 57Haabrsquos striae 57

Section II Guide 59

10 Orbit 61Diseases of the orbit 62Brachycephalic ocular syndrome 62Hornerrsquos syndrome 63Orbital cellulitis and abscess 65Orbital neoplasia 67Proptosis 68Further reading 70References 70

11 Eyelids 71Diseases of the eyelid 72Distichiasis 72Ectopic cilia 73Trichiasis 73Eyelid agenesis 75Entropion 75Ectropion 77Eyelid neoplasia 78Chalazion 79Blepharitis 80Eyelid laceration 81Further reading 82References 82

12 The third eyelid nasolacrimal system and precorneal tear film 83Diseases of the third eyelid and lacrimal system 84Third eyelid gland prolapse (ldquocherry eyerdquo) 84Third eyelid neoplasia 85Nasolacrimal duct obstruction 87Tear film disordersmdashKCS 88Qualitative tear film abnormality 88References 90

13 Conjunctiva 91Diseases of conjunctiva 91Canine conjunctivitis 91Feline conjunctivitis 93Conjunctival neoplasia 95Further reading 96References 97

14 Cornea 98Corneal diseases 99Corneal dystrophy 99

Canine keratitis 100Keratoconjunctivitis sicca (KCS) 101Pigmentary keratitis 103Pannuschronic superficial keratitis 104Corneal ulceration 105Simple corneal ulceration 105Indolent corneal ulceration 106Deep and perforating corneal ulceration 108Melting corneal ulceration 110Feline keratitis nonulcerative and ulcerative 111Feline eosinophilic keratoconjunctivitis (EK) 112Corneal sequestrum 113Further reading 114References 114

15 Anterior uvea 116Anterior uveal diseases 116Persistent pupillary membranes (PPMs) 116Uveal cysts 117Iris atrophy 118Feline diffuse iris melanoma 118Canine anterior uveal melanocytic neoplasia 119Iridociliary neoplasia 120Anterior uveitis 121Further reading 124References 124

16 Lens 125Diseases of the lens 125Nuclear sclerosis 125Cataract 126Lens subluxation and luxation 128Further reading 129References 130

17 Posterior segment 131Diseases of the posterior segment 133Asteroid hyalosis 133Collie eye anomaly 133Progressive retinal atrophy (PRA) 134Sudden acquired retinal degeneration syndrome

(SARDS) 135Retinal degeneration (excluding PRA and SARDS) 136Chorioretinitis 137Retinal detachment 138Hypertensive retinopathy 140Optic neuritis 141Further reading 142References 142

18 Glaucoma 144Glaucoma 144Further reading 148References 148

Index 149

x

Preface

Small animal general practice is a high-paced profession that requires the veterinarian to arrive at a diagnosis and formulate diagnostic and therapeutic plans within a 15- to 20-minute appointment window As a general practitioner I often found myself in this position When I did I wished for a reference where I could find a photograph similar to what I observed in the patient along with enough information to implement a plan for treatment Such scenarios provided the idea for this book The Small Animal Ophthalmic Atlas and Guide is designed as a handy reference for the busy general practitioner The bookrsquos goals are to (i) provide an extensive collection of images that practitioners can use to obtain a diagnosis during an outpatient appointment and (ii) provide just enough information about each disease relevant diagnostic tests and treatment to allow for development of a medically sound management plan

The majority of ophthalmic conditions selected for inclusion in this book are those that present frequently in general practice A smaller number of less common conditions are also included because of their significant impact on vision andor overall health of the eye The purpose of this book is not to describe every known small animal ophthalmic disease nor is it intended

to be an exhaustive review of the diseases included in the book Because this is intended to be a quick reference each chapter includes only enough background information to facilitate discussion of each ocular disease most of the information is designed to support immediate management and only select procedures are detailed step-by-step (For example detailed directions for ocular surgeries should be sought from other texts) As a guide for those who wish to delve more deeply into specific ophthalmic conditions each chapter contains a list of suggestions for further reading

Of course no reference book can be a substitute for up-to-date education sound clinical judgment and the practitionerrsquos individual knowledge of a particular patient Readers of this book should always think critically about the cases presenting to them seek advice from and make referrals to veterinary oph-thalmologists when expert care is warranted and verify that new research or information from manufacturers has not eclipsed the information in this text My hope is that this book will make it easier for practitioners to handle ophthalmic cases in their daily practice

Christine C Lim

xi

List of abbreviations

CBC complete blood countCsA cyclosporine ACT computed tomographyDNA deoxyribonucleic acidDSH domestic shorthairERG electroretinogramFeLV feline leukemia virusFIP feline infectious peritonitisFHV-1 feline herpesvirusFIV feline immunodeficiency virusIOP intraocular pressureIV intravenous

KCS keratoconjunctivitis siccaLIU lens-induced uveitisMRI magnetic resonance imagingNSAID nonsteroidal anti-inflammatory drugPLR pupillary light reflexPO by mouthPPM persistent pupillary membranePRA progressive retinal atrophyRPE retinal pigmented epitheliumSARDS sudden acquired retinal degeneration

syndromeSTT Schirmer tear test

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

Contents ix

Choroidal hypoplasia (collie eye anomaly) 55Posterior polar coloboma and choroidal hypoplasia

(collie eye anomaly) in a subalbinotic fundus 56

9 Glaucoma 57Typical appearance of acute glaucoma 57Haabrsquos striae 57

Section II Guide 59

10 Orbit 61Diseases of the orbit 62Brachycephalic ocular syndrome 62Hornerrsquos syndrome 63Orbital cellulitis and abscess 65Orbital neoplasia 67Proptosis 68Further reading 70References 70

11 Eyelids 71Diseases of the eyelid 72Distichiasis 72Ectopic cilia 73Trichiasis 73Eyelid agenesis 75Entropion 75Ectropion 77Eyelid neoplasia 78Chalazion 79Blepharitis 80Eyelid laceration 81Further reading 82References 82

12 The third eyelid nasolacrimal system and precorneal tear film 83Diseases of the third eyelid and lacrimal system 84Third eyelid gland prolapse (ldquocherry eyerdquo) 84Third eyelid neoplasia 85Nasolacrimal duct obstruction 87Tear film disordersmdashKCS 88Qualitative tear film abnormality 88References 90

13 Conjunctiva 91Diseases of conjunctiva 91Canine conjunctivitis 91Feline conjunctivitis 93Conjunctival neoplasia 95Further reading 96References 97

14 Cornea 98Corneal diseases 99Corneal dystrophy 99

Canine keratitis 100Keratoconjunctivitis sicca (KCS) 101Pigmentary keratitis 103Pannuschronic superficial keratitis 104Corneal ulceration 105Simple corneal ulceration 105Indolent corneal ulceration 106Deep and perforating corneal ulceration 108Melting corneal ulceration 110Feline keratitis nonulcerative and ulcerative 111Feline eosinophilic keratoconjunctivitis (EK) 112Corneal sequestrum 113Further reading 114References 114

15 Anterior uvea 116Anterior uveal diseases 116Persistent pupillary membranes (PPMs) 116Uveal cysts 117Iris atrophy 118Feline diffuse iris melanoma 118Canine anterior uveal melanocytic neoplasia 119Iridociliary neoplasia 120Anterior uveitis 121Further reading 124References 124

16 Lens 125Diseases of the lens 125Nuclear sclerosis 125Cataract 126Lens subluxation and luxation 128Further reading 129References 130

17 Posterior segment 131Diseases of the posterior segment 133Asteroid hyalosis 133Collie eye anomaly 133Progressive retinal atrophy (PRA) 134Sudden acquired retinal degeneration syndrome

(SARDS) 135Retinal degeneration (excluding PRA and SARDS) 136Chorioretinitis 137Retinal detachment 138Hypertensive retinopathy 140Optic neuritis 141Further reading 142References 142

18 Glaucoma 144Glaucoma 144Further reading 148References 148

Index 149

x

Preface

Small animal general practice is a high-paced profession that requires the veterinarian to arrive at a diagnosis and formulate diagnostic and therapeutic plans within a 15- to 20-minute appointment window As a general practitioner I often found myself in this position When I did I wished for a reference where I could find a photograph similar to what I observed in the patient along with enough information to implement a plan for treatment Such scenarios provided the idea for this book The Small Animal Ophthalmic Atlas and Guide is designed as a handy reference for the busy general practitioner The bookrsquos goals are to (i) provide an extensive collection of images that practitioners can use to obtain a diagnosis during an outpatient appointment and (ii) provide just enough information about each disease relevant diagnostic tests and treatment to allow for development of a medically sound management plan

The majority of ophthalmic conditions selected for inclusion in this book are those that present frequently in general practice A smaller number of less common conditions are also included because of their significant impact on vision andor overall health of the eye The purpose of this book is not to describe every known small animal ophthalmic disease nor is it intended

to be an exhaustive review of the diseases included in the book Because this is intended to be a quick reference each chapter includes only enough background information to facilitate discussion of each ocular disease most of the information is designed to support immediate management and only select procedures are detailed step-by-step (For example detailed directions for ocular surgeries should be sought from other texts) As a guide for those who wish to delve more deeply into specific ophthalmic conditions each chapter contains a list of suggestions for further reading

Of course no reference book can be a substitute for up-to-date education sound clinical judgment and the practitionerrsquos individual knowledge of a particular patient Readers of this book should always think critically about the cases presenting to them seek advice from and make referrals to veterinary oph-thalmologists when expert care is warranted and verify that new research or information from manufacturers has not eclipsed the information in this text My hope is that this book will make it easier for practitioners to handle ophthalmic cases in their daily practice

Christine C Lim

xi

List of abbreviations

CBC complete blood countCsA cyclosporine ACT computed tomographyDNA deoxyribonucleic acidDSH domestic shorthairERG electroretinogramFeLV feline leukemia virusFIP feline infectious peritonitisFHV-1 feline herpesvirusFIV feline immunodeficiency virusIOP intraocular pressureIV intravenous

KCS keratoconjunctivitis siccaLIU lens-induced uveitisMRI magnetic resonance imagingNSAID nonsteroidal anti-inflammatory drugPLR pupillary light reflexPO by mouthPPM persistent pupillary membranePRA progressive retinal atrophyRPE retinal pigmented epitheliumSARDS sudden acquired retinal degeneration

syndromeSTT Schirmer tear test

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

x

Preface

Small animal general practice is a high-paced profession that requires the veterinarian to arrive at a diagnosis and formulate diagnostic and therapeutic plans within a 15- to 20-minute appointment window As a general practitioner I often found myself in this position When I did I wished for a reference where I could find a photograph similar to what I observed in the patient along with enough information to implement a plan for treatment Such scenarios provided the idea for this book The Small Animal Ophthalmic Atlas and Guide is designed as a handy reference for the busy general practitioner The bookrsquos goals are to (i) provide an extensive collection of images that practitioners can use to obtain a diagnosis during an outpatient appointment and (ii) provide just enough information about each disease relevant diagnostic tests and treatment to allow for development of a medically sound management plan

The majority of ophthalmic conditions selected for inclusion in this book are those that present frequently in general practice A smaller number of less common conditions are also included because of their significant impact on vision andor overall health of the eye The purpose of this book is not to describe every known small animal ophthalmic disease nor is it intended

to be an exhaustive review of the diseases included in the book Because this is intended to be a quick reference each chapter includes only enough background information to facilitate discussion of each ocular disease most of the information is designed to support immediate management and only select procedures are detailed step-by-step (For example detailed directions for ocular surgeries should be sought from other texts) As a guide for those who wish to delve more deeply into specific ophthalmic conditions each chapter contains a list of suggestions for further reading

Of course no reference book can be a substitute for up-to-date education sound clinical judgment and the practitionerrsquos individual knowledge of a particular patient Readers of this book should always think critically about the cases presenting to them seek advice from and make referrals to veterinary oph-thalmologists when expert care is warranted and verify that new research or information from manufacturers has not eclipsed the information in this text My hope is that this book will make it easier for practitioners to handle ophthalmic cases in their daily practice

Christine C Lim

xi

List of abbreviations

CBC complete blood countCsA cyclosporine ACT computed tomographyDNA deoxyribonucleic acidDSH domestic shorthairERG electroretinogramFeLV feline leukemia virusFIP feline infectious peritonitisFHV-1 feline herpesvirusFIV feline immunodeficiency virusIOP intraocular pressureIV intravenous

KCS keratoconjunctivitis siccaLIU lens-induced uveitisMRI magnetic resonance imagingNSAID nonsteroidal anti-inflammatory drugPLR pupillary light reflexPO by mouthPPM persistent pupillary membranePRA progressive retinal atrophyRPE retinal pigmented epitheliumSARDS sudden acquired retinal degeneration

syndromeSTT Schirmer tear test

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

xi

List of abbreviations

CBC complete blood countCsA cyclosporine ACT computed tomographyDNA deoxyribonucleic acidDSH domestic shorthairERG electroretinogramFeLV feline leukemia virusFIP feline infectious peritonitisFHV-1 feline herpesvirusFIV feline immunodeficiency virusIOP intraocular pressureIV intravenous

KCS keratoconjunctivitis siccaLIU lens-induced uveitisMRI magnetic resonance imagingNSAID nonsteroidal anti-inflammatory drugPLR pupillary light reflexPO by mouthPPM persistent pupillary membranePRA progressive retinal atrophyRPE retinal pigmented epitheliumSARDS sudden acquired retinal degeneration

syndromeSTT Schirmer tear test

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

xii

Glossary

Accommodationmdashthe process by which the eye changes its focus (eg from near objects to far objects or vice versa)

Anisocoriamdashunequal pupil size between eyesAnterior uveamdashiris and ciliary bodyAnterior uveitismdashinflammation of the iris and ciliary bodyAphakic crescentmdashthis describes the crescent-shaped area of pupil that is

visible when the lens is subluxated or luxated It is an area of pupil that no longer has a lens in it (due to the dislocation) The borders of the aphakic crescent are the pupillary margin and the equator of the lens

Blepharitismdashinflammation of the eyelidsBlepharospasmmdashsquinting This is due to spasm of the orbicularis

oculi muscle Marked blepharospasm can cause the eyelids to roll inward (referred to as entropion)

Blood-aqueous barriermdashtight junctions within the anterior uvea which limit the entrance of blood-borne substances into the eye For example systemically administered medications may not penetrate into the eye when the blood-aqueous barrier is intact In the presence of uveitis the blood-aqueous barrier is compromised In addition to the blood-aqueous barrier anteriorly and the blood-retina barrier functions similarly posteriorly

Brachycephalic ocular syndromemdasha set of conformational abnormal-ities most commonly seen in brachycephalic dogs These abnormal-ities include bilateral exophthalmos bilateral macropalpebral fissure and bilateral medial trichiasis

Buphthalmosmdashenlargement of the eye as a result of increased intra-ocular pressure

Cataractmdashan opacity of the lens The size of the opacity can range from small and focal to encompassing the entire lens

Chalazionmdashretention of inspissated Meibomian gland secretions within the eyelid usually accompanied by eyelid inflammation

Chemosismdashedema of the conjunctivaldquoCherry eyerdquomdashthis term is used to describe prolapse of the gland of the

third eyelidChorioretinitismdashinflammation of the choroid and retina also referred

to as posterior uveitisChoroidmdashthe posterior portion of the vascular tunic of the eye also

known as the posterior uveaCiliary bodymdasha portion of the anterior uvea The ciliary body is not

visible on ophthalmic examination because it is posterior to the iris Functions of the ciliary body include aqueous humor production and accommodation and it also forms a part of the blood-aqueous barrier

Colobomamdashcongenital absence of tissue For example an optic nerve coloboma refers to an area of the optic nerve where it is missing tissue

Conjunctivitismdashinflammation of the conjunctivaCyclitismdashinflammation of the ciliary bodyCyclophotocoagulationmdashdestruction of the ciliary body with laser

energy This procedure is performed in patients with glaucoma The goal of this procedure is to decrease aqueous humor production (thereby lowering intraocular pressure)

Cycloplegiamdashparalysis of the ciliary bodyDacryocystitismdashinflammation of the nasolacrimal canaliculi and lac-

rimal sac usually due to nasolacrimal duct obstructionDistichiamdashan aberrant hair that arises from a Meibomian gland and

emerges from the Meibomian gland openingsDyscoriamdashabnormal shape of the pupilEctopic ciliummdashan aberrant hair that arises from a Meibomian gland

and emerges through the palpebral conjunctiva Because the ectopic cilium emerges through the palpebral conjunctiva it is in constant contact with the ocular surface

Ectropionmdashoutward rolling of the eyelidsElectroretingram (ERG)mdashthis is a test that measures the response of

the retina to light that is it is a test of retinal functionEnophthalmosmdashrefers to position of the globe when it is set more

posteriorly than normal within the orbitEntropionmdashinward rolling of the eyelids that results in eyelid hairs

directly rubbing against the corneaEnucleationmdashsurgical removal of the eye third eyelid conjunctiva

and eyelid marginsEpiphoramdashspillage of tears onto the faceExenterationmdashsurgical removal of all orbital contents (ie removal of

all other orbital soft tissues in addition to enucleation) This is usually performed to remove ocular or orbital neoplasia

Exophthalmosmdashrefers to position of the globe when it is set more ante-riorly than normal within the orbit

Fundusmdashthe image obtained when the posterior segment is viewed through the pupil with an ophthalmoscope The image is created by a superimposition of the retina and optic nerve upon the choroid (which includes the tapetum) and sclera

Glaucomamdashoptic nerve damage as a result of increased intraocular pressure (intraocular pressure greater than 25 mm Hg)

Goniodysgenesismdashcongenital malformation of the iridocorneal angle Also referred to as pectinate ligament dysplasia

Gonioscopymdashvisual examination of the iridocorneal angle This test is performed by a veterinary ophthalmologist It is most often used to determine if glaucoma is primary or secondary

Hyphemamdashblood in the anterior chamber Presence of hyphema indicates anterior uveitis

Hypopyonmdashpus in the anterior chamber Presence of hypopyon indi-cates anterior uveitis

Hypotonymdashdecreased intraocular pressure This is often a symptom of anterior uveitis

Iridocorneal anglemdashthe angle created by the iris and the cornea This is the main exit pathway for aqueous humor from the eye This aqueous outflow pathway is referred to as the conventional pathway

Iridocyclitismdashinflammation of the iris and ciliary bodyIridodonesismdashvisible movement of the iris seen as a result of zonular

breakdown (indicates lens instability)Keratectomymdashsurgical removal of a portion of the cornea

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

Glossary xiii

Keratitismdashinflammation of the corneaKeratoconjunctivitismdashinflammation of the cornea and conjunctivaKeratoconjunctivitis siccamdashinflammation of the cornea and conjunc-

tiva due to insufficient production of the aqueous component of the precorneal tear film This is diagnosed when the tear production is less than 15 mmmin as measured by the Schirmer tear test

Keratotomymdashincision into the cornea without removal of tissueLacrimomimeticmdashtear film substitute (artificial tears)Lagophthalmosmdashincomplete blink Lagophthalmos causes exposure

and drying of the cornea (usually the central cornea) This is a common finding in exophthalmic eyes

Luxationmdashcomplete dislocation of a structure In ophthalmology the term luxation is most often used in reference to the lens lens luxation means that the lens has completely dislocated from its normal position

Macroblepharonmdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macropalpebral fissure

Macropalpebral fissuremdashabnormally large eyelid openings This is often seen in dogs with brachycephalic ocular syndrome Also referred to as macroblepharon

Miosismdashsmall pupil due to constriction of the pupillary sphincter muscle Miosis occurs as a normal response to light It also occurs in the presence of uveitis or in response to certain drugs

Mucinomimeticmdashhaving properties similar to precorneal tear film mucin This term is used to describe how closely artificial tears approximate tears made by the body Mucinomimetic properties are desired when there is a deficiency of mucin in the precorneal tear film (a qualitative tear film abnormality)

Mydriasismdashpupil dilation as a result of constriction of the iris dilator muscle Mydriasis occurs as a normal response to decreased ambient light It also occurs as a result of retina and optic nerve disease or in response to certain medications (most notably atropine)

Nictitansmdashthe third eyelid Also referred to as the nictitating membrane

Optic neuritismdashinflammation of the optic nervePannusmdashalso referred to as ldquochronic superficial keratitisrdquo This is

immune-mediated inflammation that can involve the conjunctiva cornea and third eyelid It is commonly seen in German shepherds and related breeds

Pectinate ligament dysplasiamdashcongenital malformation of the irido-corneal angle Also referred to as goniodysgenesis

Peripapillarymdashrefers to the region of the fundus immediately sur-rounding the optic nerve

Phacodonesismdashvisible movement of the lens seen as a result of zonular breakdown (indicates lens instability)

Phthisis bulbimdashan atrophied eye This eye is smaller than normal and is no longer functional Phthisis bulbi occurs as a sequela to chronic inflammation and chronic glaucoma

Pigmentary keratitismdashthis describes a syndrome of corneal melanosis and vascularization that preferentially affects the medial and central cornea It most commonly affects dogs with brachycephalic ocular syndrome

Posterior uveitismdashinflammation of the choroid Since inflammation of the retina usually occurs in the presence of choroidal inflammation posterior uveitis usually refers to inflammation of both the choroid and the retina This is also referred to as chorioretinitis

Ptosismdashdrooping of the upper eyelid This is one abnormality consis-tently found in Hornerrsquos syndrome

Qualitative tear film abnormalitymdashdeficiency of the lipid or mucin portion of the tears

Quantitative tear film abnormalitymdashdeficiency of the aqueous portion of the tears (keratoconjunctivitis sicca)

Retropulsionmdashthis refers to gentle posteriorly directed pressure placed onto the eyes It is used to assess orbital disease Retropulsion is performed by placing the index andor middle fingers over the eyes through closed eyelids Gentle pressure is then used to push the eyes in the posterior direction (into the orbit) The amount of resis-tance by the eyes should feel equal on both sides In the presence of orbital disease the resistance noted by this action could be increased or decreased compared to normal Unilateral orbital disease will show asymmetric resistance to retropulsion

Schirmer tear test (STT)mdashthis is a measurement of tear production The test is performed by placing an STT strip (commercially avail-able adsorbent paper strip) into the ventrolateral conjunctival sac and leaving it in place for 1 minute During this minute tears are taken up by the test strip After 1 minute the strip is removed from the con-junctival sac and the length of wet strip is measured Tear production is expressed in the units of millimeter per minute Normal STT values are above 15 mmmin in the dog Schirmer tear test values are extremely variable in the cat

Sequestrummdashusually used to describe a corneal sequestrum which is necrotic corneal tissue resulting from chronic irritation This condition is most commonly seen in cats It rarely occurs in dogs

Strabismusmdashmisalignment of the eyes relative to one another Strabismus can be a congenital condition or an acquired condition For example following traumatic avulsion of the medial rectus muscle (eg following traumatic proptosis) there is unopposed action of the lateral rectus muscle This causes the direction of gaze of the affected eye to become deviated laterally

Subluxationmdashpartial dislocation of a structure In ophthalmology the term subluxation is most often used in reference to the lens lens subluxation means that the lens has partially dislocated from its normal position

Synechiamdashadhesion of the iris to an adjacent ocular structure resulting from inflammation Anterior synechia refers to an adhesion between the iris and the cornea Posterior synechia refers to an adhesion between the iris and the lens

Tapetummdashreflective layer that is part of the choroid The tapetum is found in the innermost layer of the dorsal half of the choroid

Tarsorrhaphymdasha procedure that partially or completely closes the pal-pebral fissure by suturing the upper and lower eyelids to each other

Tear film break up time (TFBUT)mdashthis measures the amount of the time the precorneal tear film remains as a stable film over the corneal surface Therefore it is a measure of tear film stability with shorter TFBUTs indicating less stability of the tear film (earlier evaporation of the tears) The TFBUT is considered an indirect measure of the mucin content of the tears Normal TFBUTs in the cat fall between 12 and 21 seconds while normal values in the dog fall between 15 and 25 seconds

Tonometrymdashmeasurement of intraocular pressureTransilluminationmdashthe act of shining light through a structure during

the ophthalmic examinationUveamdashthe vascular tunic of the eye This can be divided into the

anterior uvea (which is made up of the iris and ciliary body) and the posterior uvea (which is made up of the choroid)

Uveitismdashinflammation of all or part of the uveal tract See anterior uveitis cyclitis iridocyclitis chorioretinitis posterior uveitis

Zonulemdasha thin ligament that runs radially between the ciliary body and the lens Zonules hold the lens in correct position Breakdown of the zonules results in lens subluxation or luxation

Section i

Atlas

Section i

Atlas