Retinal Diseases

Second lecture

Etiology Extra-mural

◦ Arteriosclerosis and hypertension in elderly people. ◦ Pre-existing chronic simple glaucoma.◦ An orbital cellulitis may damp the venous return from the eye. ◦ Pressure of a sclerosed artery on the vein at an arterio-venous

crossing is a common cause of branch retinal vein occlusion Mural

◦ Diabetic retinopathy causing phlebosclerosis and a general sluggishness of the capillary and venous circulations due to the disturbed metabolism.

◦ Infective phlebitis. Intra-mural

◦ Abnormal states of blood leading to increased viscosity, polycythaemia.

◦ Infiltration of the wall of the vein by leucocytes leading to narrowing of the lumen of the vein or to clot formation.

THROMBOSIS OF THE CENTRAL RETINAL VEIN ( CRVO)

The patient, usually middle-aged and arteriosclerotic, complains of sudden diminution of vision commonly down to the perception of hand movement

he notices dark irregular patches in the centre of his field of vision (i.e. positive central scotoma).

The defective vision is often noticed by the patient when waking up in the morning, because the occlusion often takes place during sleep when the circulation becomes sluggish, the general blood pressure is lowered and the intra-ocular pressure is slightly increased.

Symptoms of Venous Occlusion

Signs of Central Retinal Vein ThrombosisSigns of Central Retinal Vein Thrombosis

There are no external signs except that the pupillary reaction to direct light may be a little sluggish. The ophthalmoscopic picture is very characteristic :

There are no external signs except that the pupillary reaction to direct light may be a little sluggish. The ophthalmoscopic picture is very characteristic :

The fundus appears splashed with haemorrhages radiating from the disc in all directions. The retinal veins are grossly distended and tortuous.

The fundus appears splashed with haemorrhages radiating from the disc in all directions. The retinal veins are grossly distended and tortuous.

The arterioles are slightly narrowed and may be concealed by oedema and haemorrhages. Patches of white exudate may appear among the haemorrhages.

The arterioles are slightly narrowed and may be concealed by oedema and haemorrhages. Patches of white exudate may appear among the haemorrhages.

Increased extravascular

pressure

Oedema and

haemorrhage

Hypoxia

Stagnation

Venous Occlusion

1. Secondary Neovascular Glaucoma. 1. Secondary Neovascular Glaucoma.

2. Vitreous Haemorrhage. 2. Vitreous Haemorrhage.

3. Tractional Retinal Detachment.3. Tractional Retinal Detachment.

TreatmentTreatment

The primary systemic causative conditions should always receive appropriate attention. Unfortunately, there is no effective treatment once the blockage has become fully established. If the patient is seen within a few hours of the onset of symptoms, the administration of anticoagulants may be effective in maintaining the circulation and preventing the spread of the thrombotic process. This anticoagulant treatment must be controlled by prothrombin estimation.

The primary systemic causative conditions should always receive appropriate attention. Unfortunately, there is no effective treatment once the blockage has become fully established. If the patient is seen within a few hours of the onset of symptoms, the administration of anticoagulants may be effective in maintaining the circulation and preventing the spread of the thrombotic process. This anticoagulant treatment must be controlled by prothrombin estimation.

Complications

Anticoagulants should be employed with care in arteriosclerotic patients.

However, there is no guarantee of improvement with the administration of anticoagulants or steroids.

If fluorescein angiography reveals widespread capillary occlusion and retinal ischaemia, Laser treatment (panretinal photocoagulation –PRP) is of benefit in treating the retinal complications of the ischaemic response and aborting the development of neovascular glaucoma and rubeosis iridis.

Treatment cont-

Essential hypertension is associated with thickening of the arteriolar wall as a result of hypertrophy of muscle fibres in the media and increase of fibrous tissue in the intima.

Sustained elevation of blood pressure leads to necrosis of the vascular smooth muscle and leakage of plasma into the unsupported vessel wall through a damaged endothelium which eventually results in secondary vascular occlusion.

The changes that occur in the retina in hypertension are primarily vascular due to the persistently elevated diastolic blood pressure. The retinal changes depend on the state of the retinal vessels prior to the development of hypertension and to some extent on any associated retinal damage, as for example in malignant hypertension.

The primary response of healthy retinal arterioles to systemic hypertension is spasm leading to narrowing.

HYPERTENSIVE RETINOPATHY

Hypertensive retinopathy

Cotton-wool spots and macular star

Disc oedema

Focal Generalized

Arteriolar constriction

Extravascular signs

Flame-shaped retinal haemorrhages

Arteriolosclerosis (A-V changes)

Grading of arteriolosclerosis

Diabetic retinopathy is essentially a microangiopathy affecting the retinal precapillary arterioles, capillaries and venules. The retinopathy is the result of two mechanisms :

Microvascular Occlusion.—This is due to thickening of the capillary basement membrane, endothelial proliferation, deformation of the red blood corpuscles and increased stickness

of the platelets. The microvascular occlusion leads to retinal capillary non-perfusion and retinal ischaemia which cause the formation of A/V shunts and neovascularisation.

Microvascular Leakage.—This is due to reduction in the number of mural cells of the capillary wall leading to microaneurisms as a result of local capillary distensions, diffuse retinal oedema due to extensive capillary leakage and/or localised retinal oedema due to focal leakage from microaneurysms.

Diabetic retinopathy

Pathogenesis of diabetic retinopathy

Occlusion

Leakage

Consequences of retinal ischaemia

Adverse Risk Factors

1. Long duration of diabetes 2. Poor metabolic control 3. Pregnancy 4. Hypertension 5. Renal disease 6. Other Obesity Hyperlipidaemia Smoking Anaemia

Consequences of chronic leakage

Ophthalmoscopically, the earliest changes of background diabetic retinopathy characteristically affect the smaller blood vessels. The retinopathy is characterised by :

1. Presence of Microaneurysms.—They are located in the inner nuclear layer of the retina and appear as small round dots, usually located temporal to the macula.

2. Venous Dilatations and Beading.— A common and early finding is dilatation of veins with marked irregularity in caliber that gives rise to beading and loop formation.

3. Retinal Hemorrhages. —The shape of the haemorrhages depend on their location within the retina :-◦ i) Dot and Blot haemorrhages denote hasmorrhage in mid retina.◦ ii) Flame-shaped haemorrhages denote haemorrhage in nerve

fibre layer. ◦ iii) Red patch with fluid level

Background Diabetic Retinopathy Clinical Picture

4. Yellow Waxy Hard Exudates. — They are composed of lipoprotein and lipid-laden macrophages. The exudates are located between the inner plexiform and inner nuclear layers of the retina. They appear as yellow-white refractile deposits, particularly in the region of the macula.

5. Retinal oedema.—This is due to increased permeability of the retinal capillaries and is characterized by retinal thickening obscuring the underlying choroidal pattern.

 

Location of lesions in background diabetic retinopathy

Signs of background diabetic retinopathy

Microaneurysms usually temporal to fovea Intraretinal dot and blot haemorrhages

Hard exudates frequentlyarranged in clumps or rings

Retinal oedema seen asthickening on biomicroscopy

Preproliferative Diabetic Retinopathy.— characterised by :

2. Intraretinal Microvascular Abnormalities; IRMA resembling flat retinal revascularization.

4. Arteriolar Narrowing.5. Large Dark Blot Haemorrhage.

1. Cotton-Wool Patches. —They are microinfarction of ganglion cells due to capillary occlusion in the nerve fiber layer.

3. Dilatation of Retinal Veins with marked irregularity in caliber giving rise to beading and loop formation.

Preproliferative diabetic retinopathy

Treatment - not required but watch for proliferative disease

• Cotton-wool spots• Venous irregularities

• Dark blot haemorrhages• Intraretinal microvascular abnormalities (IRMA)

Signs

1. Neovascularisation.— New vessels may proliferate on the optic disc and along the course of the major temporal arcade. The predilection for revascularization at the optic disc may be explained by the absence of internal limiting membrane over the optic nerve head. The new vessels start as endothelial proliferations arising from the veins and are enveloped in fibrovascular epiretinal membrane which has the potential to contract.

2. Fibrovascular Tissue Proliferation. —Fibrovascular networks become adherent to the posterior vitreous face and continue to proliferate with increased tendency to bleeding.

3. Recurrent Vitreous Haemorrhage. —This leads to shrinkage of the vitreous and promotion of tractional retinal detachment.

Proliferative Diabetic Retinopathycharacterised by :

Proliferative diabetic retinopathy

• Flat or elevated• Severity determined by comparing with area of disc

Neovascularization

Neovascularization of disc = NVD

• Affects 5-10% of diabetics• IDD at increased risk (60% after 30 years)

Neovascularization elsewhere = NVE

Medical Treatment.—Although there is no medical cure for diabetic retinopathy, the following therapeutic measures may be helpful in minimising complications :

Control of Blood Sugar. Control of Systemic Blood Pressure. Decrease of Platelets Stickiness. —Acetyl

salycilic acid may help in decreasing platelet stickiness.

Treatment of Anaemia.—

Diabetic Maculopathy.—Focal or grid pattern argon laser photocoagulation is

Treatment of Diabetic Retinopathy

Ocular Treatment.—This depends on the clinical presentation :

Background Diabetic Retinopathy. —No treatment is indicated unless central vision is threatened. Diabetic Maculopathy.—Focal or grid pattern argon laser photocoagulation is recommended for focal or diffuse maculopathy respectively.

Proliferative Diabetic Retinoapthy.—Panretinal argon laser or xenon arc photocoagulation is the recommended method of treatment. The aim of photocoagulation is to induce involution of retinal neovascularisation, hence reducing the incidence of vitreous haemorrhages.

Tractional Retinal Detachment. —This is treated by pars plana vitrectomy, pealing of preretinal membranes and endophotocoagulation.

RETINOPATHY IN TOXEMIA OF PREGNANCY

Toxaemia of pregnancy (PET) is a syndrome occurring after the sixth month of pregnancy, and characterized clinically by hypertension, generalized oedema and proteinuria that may culminate in convulsions and coma.Clinical Picture.—The patient may complain of spots or flashes of light before the eyes, impairment of vision and headache.The clinical course of the disease may be divided into three stages :

1. Stage of functional spasm of arterioles.2. Stage of organic sclerosis of arterioles throughout the body.3. Stage of retinopathy characterized by striate haemorrhage, fluffy exudates, papilloedema with posterior pole neuroretinal oedema, and peripapillary serous choroidal and retinal detachment.

General Signs.— Hypertension, albuminuria, oedema of the legs and haematuria are usually present.Ocular Signs. —characteristic fundus picture comprises generalized narrowing and localized constrictions of the arterioles, few cotton wool patches, superficial haemorrhages, and slight oedema of the retina and optic disc resembling hypertensive retinopathy.

Treatment.—Termination of pregnancy and management of the toxemic state should be urgently considered.

Retinal detachment, (more accurately retinal separation) , is a condition in which the sensory retina is separated from the underlyingretinal pigment epithelium (RPE )at the line of cleavage between the layer of visual receptors and the pigment epithelium, with an accumulation of fluid in the potential space between them.

The fluid may accumulate between the sensory retina and RPE by any of the following mechanisms :

Escape of fluid from the vitreous cavity into the subretinal space through a retinal hole or break.

Extravasation of fluid from the choroid or the retina.

Pulling on the retina by a vitreo-retinal band of fibrous adhesion.

RETINAL DETACHMENT

1. Flashes of Light. —Flashes perceived as flickers of light are initially observed in the direction opposite the site of the retinal tear. They are due to irritation of the rods and cones by the pull on the retina by adhesion bands.2. Floaters. —A floater is a moving vitreous opacity that casts a shadow on the retina. The floaters appear as dark spots before the eye. Floaters which are persistent in the visual field, in a myopic patient, should arouse suspicion of retinal detachment.3. Field Defect.—A curtain, a cloud or a shadow appears in the visual field corresponding to the extent and position of the detachment.4. Failing Vision.—A loss of central vision is observed when the macula is detached.

Symptoms of Retinal Detachment

1- can be an isolated condition, inherited as an autosomal recessive, autosomal dominant, or X-linked recessive trait.

2- The changes of retinitis pigmentosa can also be seen in a number of ocular, central nervous system, and systemic conditions.

 ClinicallyIn primary retinitis pigmentosa the manifestations are least

severe in the autosomal dominant form and most severe in the X-linked form.

In all patients, an early symptom is decreased night vision. Gradually, the visual fields become more constricted.

The fundus shows the characteristic spicule arrangement of pigment, waxy pallor of the optic disc, and marked attenuation of the arterioles.

Female carriers of the X-linked form can have normal fundi or patchy involvement of the fundus with some visual reduction. 32

HEREDITARY RETINAL DYSTROPHIES RETINITIS PIGMENTOSA

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RETINITIS PIGMENTOSA

a primary malignant intraocular neoplasm that arises from immature retinoblasts within the developing retina.

It is the most common primary intraocular malignancy of childhood, occurring in about 1 of 15,000 children

Most cases occur in children younger than 6 years of age.

The neoplasm has strong tendencies to invade the brain via the optic nerve and to metastasize widely

Approximately 60% to 70% of retinoblastoma cases are unilateral.

The most common presenting symptom of retinoblastoma is

1-leukokoria, a white pupil, in the tumor-containing eye or eyes.

2-strabismus (i.e., esotropia or exotropia) and symptomatic or asymptomatic visual impairment.

3-Less common presenting symptoms include a red eye, a cloudy cornea, or a change in color of iris, and pain in or around the eye.

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Retinoblastoma.

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Retinoblastoma.

Classically, ROP develops in premature infants who have received supplemental oxygen therapy. Infants weighing less than 1500 g at birth and those born at a gestational age of less than 32 weeks are at risk for developing ROP..

Vascular proliferation and secondary vitreous fibrosis are thought to result from the effect of increased oxygen levels on the immature, incompletely vascularized retina.

ROP typically arises in the temporal quadrant of the retina, because the temporal retina usually is not completely vascularized at term, especially in premature infants.

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RETINOPATHY OF PREMATURITY (ROP)

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RETINOPATHY OF PREMATURITY

Wright interactive ophthalmology.By K.Wright ,1997 on CD. Lecture notes in ophthalmology.By Bruce James…ninth edition,2003,Blackwell

publications. Duane's ophthalmology ,basic science,on

CD,2003 Clinical ophthalmology. Kanski Tutorial.2007

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References.

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