SUBJECT: Ophthalmology TOPIC: Ocular media, binocular visionLECTURER: ?SHIFTING/DATE: September 11, 2008TRANS GROUP: a-k-r

I. Ocular Media Cornea- constant refractive power of 43 diopters (38-47D) Lens- refractive power 17 diopter (12-22D) Total refractive power- 60 diopters

*vitreous- minimal contribution of dioptersII. Diopter

- unit of lens power- lens with 1 DO of power will bring parallel rays of light to a focus

at distance of 1 meter*Formula: D=1/feg. 2 DO= 50cm or 0.5m

III. Refractive States of the Eye Emmetropia- parallel rays of light brought to focus on retina Ametropia- condition where parallel rays of light are brought

to focus behind, in front or at 2 planes of retina

IV. Types of Ametropia Hyperopia (far-sighted) Myopia (near-sighted) Astigmatism

V. Hyperopia- rays of light not refracted enough- point of focus is behind the retina - short eye- AP diameter or axial length is in range of 21mm-22.75mm-normal length 23mm to 23.75mm

Other Features: Glaucoma may develop Anterior chamber is shallow, pupils smaller, optic nerve

small Pseudopapilledema or pseudo-optic neuritis may be present

Signs and Symptoms: BOV especially at near vision Headache, frontal in origin Sensitive to light

Correction: Use of plus (+) lenses or biconvex lenses

VI. Special Types of Hyperopia1. Aphakia

-absence of crystalline lens (congenital)-blurring at far and near vision-iridodonesis: nothing holding or pushing the iris-surgical removal of lens as in cataract extraction-Tx: high plus (+) lenses or convex lenses

2. Lens Dislocation/Subluxation- complete or partial -crystalline lens subluxate upward due to congenital weakness of the zonular fibers, hence, stronger zonule will pull lens up. - Subluxate downward as seen in trauma

Other conditions: Homocysteinuria- disclocation is superior and nasal Marfan’s syndrome- disclocation is superior and temporalSigns and Symptoms:

Same with aphakia, monocular diplopia may be experienced

Treatment Use of corrective lenses: plus (+) lenses Surgical removal of crystalline lens Mioticconstrict pupil to focus patient’s sight

3. Presbyopia- decrease power of accommodation- usually occurs when a patient reaches 42 yo

Signs and Symptoms: Blurring or inability to read fine prints

Treatment Use of convex lenses

VII. Myopia- Parallel rays of light focus in front of retina- Excessive refractive power- Eye is long- AP diameter or axial length about 24 to 26mm- Increase in curvature of the lens- see incipient cataract may

develop “secondary sight”- Elevated blood glucose level myopic changes in the

index of refraction- AC is deep, pupils are wide, fundus appears bigger and

myopic crescentSigns and Symptoms:

Poor vision for far with good vision for near Holds reading material close to the face

Treatment Use of concave lenses (minus lens) Choroid appears black

VIII. Accommodation- Flexible mechanism by which the eye changes refractive

power due to changes in shaoe of the crystalline lens- Results from an innervational stimulus producing an increase

tonicity of ciliary muscle and relaxation of zonules allowing elasticity of lens to assure a more biconvex state and produce a greater refractive power

- Consist of vertical and horizontal meridian

MARY YVETTE ALLAIN TINA RALPH SHERYL BART HEINRICH PIPOY TLE JAM CECILLE DENESSE VINCE HOOPS CES XTIAN LAINEY RIZ KIX EZRA GOLDIE BUFF MONA AM MAAN ADI KC PENG KARLA ALPHE AARON KYTH ANNE EISA KRING CANDY ISAY MARCO JOSHUA FARS RAIN JASSIE MIKA SHAR ERIKA MACKY VIKI JOAN PREI KATE BAM AMS HANNAH MEMAY PAU

RACHE ESTHER JOEL GLENN TONI

SUBJECT: optha TOPIC: ocular media and binocular vision

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***circle of least confusion: focusing of iris (like a camera)

IX. Astigmatism- Light rays entering eye focus on 2 separate lines instead of a

point- Light is not refracted equally on all meridians- Sometimes clear vision, sometimes blurred vision- Blurred vision: only complaint in higher astigmatism error- Tilting of head: 2nd most frequent complaint in high degrees

of oblique astigmatism- Narrowing of the eyelids to achieve a pinhole or stenopeic

effect- Squints both for distance and near task- Frontal headaches are common- Test by using astigmatic clock (five finger) or dial (circle)

X. Types of Astigmatism1. Simple hyperopic astigmatism (SHA)

-focus of light rays one behind and one above the retina2. Simple myopic astigmatism (SMA)

-focus of light rays one in front and one above the retina 3. Compound hyperopic astigmatism (CHA)

-focus of light rays both behind the retina but in different levels

4. Compound myopic astigmatism (CMA)-focus of light rays both in front of the retina but in different levels

5. Mixed astigmatism (MA)-focus of light rays on top of retina in two different degrees-surgical

XI. Method of Refraction1. Subjective Method

-utilize individual’s ability to choose the lens-utilizes a set of Trial lenses -patient must be intelligent-trial and error

2. Objective Method-uses retinoscope-useful in children, decreased IQ, unconscious or semi-conscious-see vertical or horizontal light

3. Cycloplegic Method-drugs used to paralyze accommodation power of ciliary body such as:

Atropine 1% Tropicamide 0.5% Cyclopentolate and homatropine (2%)

-routinely done in children <6yo-utilizes the objective method which uses a retroscope to accurately measure refractive error

XII. Types of Optical Lenses Used Glasses and plastic lenses Contact lenses

o Extended wear contact lenso Daily wear contact lenso Rigid gas permeable contact lenso Toric contact lens: expensiveo Astigmatism correction ≥100

Intraocular lenses

o Specializedo Polymethacrylate o Silicon polymethacrylate o Hydrogelso Become more inerto Causes lot of reactions: uveitis

XII. Other modalities of correcting Refractive errors Photorefractive Keratectomy (PRK) Laser-in-situ keratomileusis (LASIK) Intracorneal lens Implantable contact lens Radial Keratotomy (R.K.)

**Radial Keratotomy is an established surgical procedure whose purpose is to remove or reduce ametropia resulting from myopia and/or myopic astigmatism. The whole point of RK is to reduce the central corneal curvature sufficiently so as to move the

cornea's focus back onto the retina

I. Anatomy of Extraocular muscle and inner fascia 3 pairs of EOM

o Horizontal – medial and lateral rectio Vertical – superior and inferior rectio Oblique – superior and inferior obliques

II. Nerve Supplya. Lateral rectus – CN 6 (Abducens)b. Superior oblique – CN4 (Trochlear)c. The rest of the EOM are supplied by CN3

i. Upper division (levator palpabrae muscle & Superior rectus)

SUBJECT: optha TOPIC: ocular media and binocular vision

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ii. Lower division (Medial rectus, inferior rectus, inferior oblique)

o The parasympathetic innervations to the spinchter papillae and ciliary muscle travels with the branch of the lower division of the occulomotor nerve which supplies the inferior oblique muscle

o Formula: LR6SO4III. Horizontal rectus muscles

Medial and lateral rectus muscles – arise from annulus of zinn, course along the medial and lateral orbital wall and inserts 5.5mm and 7mm from the limbus, respectively

IV. Vertical Rectus muscles

Superior rectus and inferior rectus muscles Superior rectus muscle originates from the

Annulus of Zinn, courses anteriorly, upward over the eyeball and laterally, forming an angle of 23° with the visual axis of the eye in primary position.

It inserts 7.7mm from the limbusa. Superior rectus

i. Primary action- elevationii. Secondary action- adduction and

incycloductinb. Inferior rectus

i. Primary- depressionii. Secondary- adduction and

excycloductionV. Oblique muscles

Superior oblique muscle o originate from the annulus of zinn and passes

anteriorly and upward along the superomedial wall of the orbit becoming tendinous before passing through the trochlea located on the nasal side of the superior orbital rim. The tendon is reflected inferiorly, posteriorly and laterally, forming an angle of 51° with the visual axis of the eye and inserts in the posterosuperior temporal quadrant of the yeball passing to the SR muscle

o Primary action – incycloductiono Secondary action – depression and abduction

Inferior oblique muscle o originates from the periosteum of the maxillary

bone, just posterior to the orbital rim and lateral to the orifice of lacrimal fossa. It passes laterally,

superiorly and posteriorly, going to the inferior rectus and under the lateral rectus to insert in the posterolateral position of the globe. It forms an angle of 51° with the visual axis n primary position

o primary action: excycloductiono secondary: elevation and abduction

**ANNULUS OF ZINN – holds EOM together except IO

VI. Rectus muscle insertion relationship The rectus muscle tendons insert progressively further

from the limbus in the orders of the medial rectus, inferior rectus, lateral rectus, superior rectus, by drawing a continuous curve which asses through these insertions, one obtains a spiral, known as the spiral of Tillaux

VII. Blood supply of the EOM

Most important blood supply – medial and lateral muscular branches of the ophthalmic artery

Lateral muscular branch supplies LR, SR, SO and LPS Medial muscular branch supplies IR, MR and IO Lacrimal artery partially supplies the lateral rectus and

the infraorbital artery partially supplies the IO and IR muscles

7anterior cilliary arteries accompanying the 4rectus muscles and each muscle has 2 anterior ciliary arteries except the lateral rectus with only 1 artery

Venous system empties into the superior and inferior orbital veins there are 4vortex veins and located

SUBJECT: optha TOPIC: ocular media and binocular vision

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posterior to the equator near the nasal and temporal margins of the SR and IR muscles

There is a high ratio of nerve fibers to eye muscle fibers (1:3 to 1:5) than in skeletal muscle which has a low ratio of (1:50 to 1:25)

VIII. Tenon’s capsule (Fascia Bulbi) This is an envelope of elastic connective tissue which is

attached to the optic nerve posteriorly and becomes fused with the intermuscular membrane 3mm from the limbus

o Posterior Tenon’s capsule – is a fibrous condensation that separates the orbital fat inside the muscle cone from the sclera, keeping the sclera fat-free

o Anterior Tenon’s capsule – extends forward over the muscle and separates them from the orbital fat and structure lying outside the muscle cone

IX. Sherrington’s law of reciprocal innervations States that increased innervations and contraction of a

given EOM is accompanied by a reciprocal decrease in innervations of its antagonist

X. Version and Vergence Heering’s Law of Motor correspondence – states that

the equal and simultaneous innervations flow to synergistic muscle concerned with the desired direction of gaze. This is particularly useful on binocular eye movement and evaluating yolk muscles.

When the eye movement is conjugate and the eyes more in the same direction, it is known as VERSION. When the eye movement are disconjugate and the eyes move in opposite direction, the movement is called VERGENCE

YOLK MUSCLES – describes 2 muscles one from each eye which are the prime movers of their respective eyes in a given position of gaze.

XI. Binocular Vision1. Corresponding Retinal Points

The foveas are the most important corresponding retinal areas due to their high resolving power

Associated with foveal fixation2. Fusion:

The cortical unification of visual objects into a single percept

For retinal images to be fused, they must be similar in size and shape

3. Depth perception and stereognosis Depth perception is the monocular sensation of depth

1. ophthalmic artery, 2. central retinal artery, 3. ciliary arteries, 4. two long posterior ciliary arteries, 5. short posterior ciliary arteries. 6. long posterior ciliary arteries travel in the suprachoroidal space anteriorly then supply the choroid anteriorly via recurrent branches, 7. posterior ethmoidal, 8. anterior ethmoidal vessels, 9. superior oblique muscle

SUBJECT: optha TOPIC: ocular media and binocular vision

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Stereognosis is the binocular sensation of relative depth covered by horizontal retinal image

XII. Abnormalities of Binocular Vision1. Diplopia

Is a result from a misalignment of the visual axes, wherein an image falling on the fovea of one eye and simustaneously on a non-foveal point in the other eye

2. Suppression Is the alteration of the visual sensation that results from

the images of one eye being inhibited or prevented from reaching consciousness

3. Ambiyopia Is a unilateral or bilateral reduction of corrected central

visual acuity without a visible organic lesions commensurals with this loss

XIII. Classification of StrabismusA. Fusional Status

1. Orthophoria-ideal ocular balance2. Heterophoria-deviation kept latent by fusional

mechanism3. Heterotropia-deviation which is manifest at all times

B. Variation of the deviation with gaze1) Comitant- deviation does not vary with direction of gaze2) Incomitant- deviation does vary with direction of gazeC. According to fixation:1. Alteranting- spontaneous alterantion of fixation2. Monocular- definite preference of fixationD. Age of onset1. Congenital-ocular deviation occurs prior to age 6 months2. Acquired- ocular deviation occurs after to age 6 monthsXIV. Evaluation of Strabismus History Visual acuity Ocular Alignment

- Monocular cover-uncover test- Alternate cover test- Simultaneous prism cover test

Corneal Light reflex test- Hirschberg’s method- Modified krimsky’s tets- Ambiyoscope

Disimilar Image test- Maddox rod test- Double Maddox rod test- Red filter test

Special Motor test- Forced duction test- Active force generated test- Saccadic velocity

Refraction- Cycloplegic refraction- Manifest refraction

Pseudostrabismus- due to broad nasal bridge and often associated with epicanthal folds

XV. EsodeviationA. Congenital1. Congenital or infantile esotropia-onset of the esotropia at birth- Documented presence at six month of age- Family history of genetic patterns are unusual- Seen in children with cerebral palsy and hydrocephalus- Treatment: full cycloplegic refraction and surgery by 18th

month of age

2. Early onset esodeviation with accommodative component- Common type of esodeviation- Majority of patients have both an accommodative and a

non-accomodative component- Also called mixed mechanism- Treatment: when after full hyperopic correction- Surgery is considered. The non-accomodative is

managed surgically.3. Duanes syndrome

- Assocaiated with other congenital abnormalties such as:

- Goldenhar’s syndrome- Mobius syndrome- Klippel-feil syndrome- Treatment: full refractive correction and surgery Type I: Limitation of abduction- most commonly seen

and frequently affecting the left eye Type II: Limitation of adduction Type III: Limitation of abduction and adduction

B. Acquired1. Comitant accomodative esotropia

- Onset is from 6 months to 7 years with an average of 2 ½ years

- Aften hereditary- Ambitopia is frequent, with no diplopia

SUBJECT: optha TOPIC: ocular media and binocular vision

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- Refractive accommodative, Non-refractive accommodative and combined form or mixed mechanism esotropia are some of the types.

2. Non- accommodative esotropia- Stress induced and can be precipitated by debilitating

illness, emotional trauma, physical injury and ageing- Can be cyclic or have a variable cycle of 24-48 hours- Treatment: full hyperopic correction. Some require

surgery when they progress to cyclic deviation3. Incomitant esotropia

- Medial rectus muscle restriction such as in thyroid myopathy, medial orbital wall fracture, excessively resected medial rectus muscle

- Lateral rectus muscle weakness as seen in abducens palsy

Moments with 3b =)

yes parang model lang… hehehe

Moments daw oh…

Happy =) sad =(

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