Ординатура / Офтальмология / Английские материалы / Ophthalmology A Short Textbook_Lang_2000

macular involvement (i.e., the initial detachment included the macula), a loss of visual acuity will remain. The prognosis for the other forms of retinal detachment is usually poor, and they are often associated with significant loss of visual acuity.

12.4.2Degenerative Retinoschisis

Definition

A frequently bilateral split in an inner and outer layer of the retina. The split is usually at the level of the outer plexiform layer (Fig. 12.25).

Epidemiology: About 25% of all people have retinoschisis. The tendency increases with age.

Pathogenesis: Idiopathic retinal splitting occurs, usually in the outer plexiform layer.

Symptoms: Retinoschisis is primarily asymptomatic. The patient will usually notice a reduction of visual acuity and see shadows only when the retinal split is severe and extends to the posterior pole.

Diagnostic considerations: Ophthalmoscopic examination will reveal bullous separation of the split inner layer of the retina. The inner surface has the appearance of hammered metal. Rarely breaks will occur in the inner and outer retinal layers.

Retinoschisis.

Fig. 12.25 Split in the retina with bullous separation of the inner layers of the retina (arrows).

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Differential diagnosis: Rhegmatogenous retinal detachment should be excluded. Ophthalmoscopy will reveal a continuous break in the retina in a retinal detachment, and the retina will not appear as transparent as in retinoschisis. However, retinal breaks can also occur in retinoschisis. In the inner layer of the retina, these breaks will be very small and hardly discernible. In the outer layer, they will be very large. Complete rhegmatogenous retinal detachment can occur in retinoschisis only where there is a break in both layers.

Treatment: Usually no treatment is required. The rare cases in which retinal detachment occurs are treated surgically using the standard procedures for retinal detachment.

Degenerative retinoschisis differs from retinal detachment in that it usually requires no treatment.

Clinical course and prognosis: The prognosis for degenerative retinoschisis is very good. Progressive retinal splitting or retinal detachment with a subsequent reduction in visual acuity is rare.

12.4.3Peripheral Retinal Degenerations

Definition

Peripheral retinal degenerations refer to degenerative changes that lie parallel to the ora serrata in the peripheral portions of the retina. These include two basic types:

Harmless retinal changes such as pars plana cysts of the posterior ciliary body or peripheral chorioretinal atrophy (cobblestone degeneration).

Precursors of retinal detachment such as local thinning of the retina referred to as snail track or lattice degeneration.

Epidemiology: The prevalence of the lesions is 6–10%.

Pathogenesis: Unknown.

Symptoms: Peripheral retinal degenerations are asymptomatic.

Diagnostic considerations: The diagnosis is made by ophthalmoscopic examination of the peripheral retina with the pupil dilated. The retina may be examined by indirect binocular ophthalmoscopy or using a three-mirror lens.

Cobblestone degenerations appear as whitish sharply defined localized areas of extensive atrophy of the retina, pigment epithelium, and choriocapillaris that lie between the ora serrata and the equator. Snail track degeneration presents with yellowish, whitish radiant dots consisting of microglia and astrocytes. Lattice degeneration presents with thinned retinal areas with whitish sclerotic vessels. This results in reactive focal atrophy and hypertro-

phy of the retinal pigment epithelium in the region of equatorial degeneration and liquefaction of the overlying vitreous body.

Differential diagnosis: The findings are highly characteristic and easily diagnosed clinically. Rarely, vascular processes or inflammatory changes and scars from other causes must be considered in a differential diagnosis.

Treatment: Treatment is either not required or not recommended as laser therapy does not reduce the risk of retinal detachment. Ophthalmoscopic fol- low-up examinations should be performed at regular intervals.

Prophylaxis: No prophylaxis is possible.

Clinical course and prognosis: The clinical course is usually benign. Round atrophic retinal breaks can develop in the areas of snail track and lattice degeneration. However, the long-term risk of retinal detachment is only 1%.

12.4.4Central Serous Chorioretinopathy

Definition

Serous detachment of the retina and/or retinal pigment epithelium.

Etiology: Serous detachment occurs through a defect in the outer blood – retina barrier (“tight junctions” in the retinal pigment epithelium). Local factors that may be related to physical or psychological stress are presumably involved.

Epidemiology: The disorder primarily affects men in the third and fourth decade of life.

Symptoms: Patients present with a loss of visual acuity, a relative central scotoma (dark spot), image distortion (metamorphopsia), or perception of objects as larger or smaller than they are (macropsia or micropsia).

Diagnostic considerations: Ophthalmoscopy will reveal a serous retinal detachment, usually at the macula. In chronic cases, a fine brown and white pigment epithelial scar will develop at the site of the fluid effusion. Swelling in the central retina shortens the visual axis and produces hyperopia. The site of fluid effusion can be identified during the active phase with the aid of fluorescein angiography (Fig. 12.26a and b).

Treatment: Usually no treatment is required for the first occurrence of the disorder. Retinal swelling resolves spontaneously within a few weeks. Recurrences may be treated with laser therapy provided the site of fluid effusion lies outside the fovea centralis. Corticosteroid therapy is contraindicated as the therapy itself can lead to development of central serous chorioretinopathy in rare cases.

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Central serous chorioretinopathy.

Fig. 12.26

a Bullous fluid accumulation beneath the retina (arrows).

b Angiogram of the same patient. The site of fluid effusion appears as a hyperfluorescent spot (arrow).

Clinical course and prognosis: The prognosis is usually good. However, recurrences or chronic forms can lead to a permanent loss of visual acuity.

Local stress-related factors and steroids can lead to macular edema in predisposed patients.

12.4.5Age-Related Macular Degeneration

Definition

Progressive degeneration of the macula in elderly patients.

Epidemiology: Age-related macular degeneration is the most frequent cause of blindness beyond the age of 65 years.

Pathogenesis: Drusen develop in the retinal pigment epithelium due to accumulation of metabolic products.

Symptoms: Patients notice a gradual loss of visual acuity. Where macular edema is present, patients complain of image distortion (metamorphopsia), macropsia, or micropsia.

Findings and diagnostic considerations: Ophthalmoscopic examination can distinguish two separate stages that occur in chronological order (Table 12.6).

Differential diagnosis: Other vascular diseases of the retina such as branch retinal vein occlusion should be excluded by ophthalmoscopy. Malignant melanoma should be excluded by ultrasound studies.

Treatment: No reliably effective medical therapy is available. Laser therapy may be performed in the exudative stage in about 5–10% of all patients without neovascularization involving the fovea centralis. Use of progressively stronger near vision aids such as a hand magnifier or binocular magnifier should be tried.

Clinical course and prognosis: The course of the disorder is chronic and leads to progressive loss of visual acuity.

Laser therapy may be performed in the exudative stage of late agerelated macular degeneration in 10% of all patients provided the disorder is diagnosed early.

Table 12.6 Stages of age-related macular degeneration (ARM)

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Stages of late age-related macular degeneration.

Fig. 12.27

a Late age-re- lated macular degeneration:

Typical signs include drusen (arrow) and geographically central atrophy (arrowhead).

b Late agerelated macular degeneration: Intraretinal bleeding (arrow) is a typical sign.

c Late age-related macular degeneration: The fibrous scar is a typical sign.

12.4.6Degenerative Myopia

Definition

The fundus in degenerative myopia is characterized by abnormal chorioretinal atrophy.

Epidemiology: Chorioretinal atrophy due to myopia is rare.

Pathogenesis: The atrophy usually occurs in the presence of severe myopia exceeding minus 6 diopters. The causes include stretching changes in the retina, choroid, and Bruch's membrane due to the elongated globe in axial myopia.

Symptoms: Loss of visual acuity occurs where there is macular involvement.

Findings and diagnostic considerations: Typical signs include chorioretinal atrophy around the optic disk and at the posterior pole and defects in Bruch’s membrane known as lacquer cracks (Fig. 12.28). These cracks can provide openings for vascular infiltration with resulting subretinal neovascularization that can lead to retinal edema and bleeding (Fuchs’ black spot). The final stage of the disorder is characterized by a diskiform scar. The diagnosis is made by ophthalmoscopy. Fluorescein angiography is indicated where subretinal neovascularization is suspected.

Differential diagnosis: Choroidal scars and angioid streaks (breaks in Bruch’s membrane) in pseudoxanthoma elasticum must be excluded by ophthalmoscopy. The diagnosis is unequivocal where myopia is present.

Degenerative myopia.

Fig. 12.28 Extensive areas of chorioretinal atrophy (arrows).

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Treatment: The causes of the disorder cannot be treated. It is important to correct myopia optimally with eyeglasses or contact lenses to avoid fostering progression of the disorder. Subretinal neovascularization outside the fovea or close to its border can be treated by laser photocoagulation.

Clinical course and prognosis: Chronic progressive myopia will result in increasing loss of visual acuity. The prognosis for subretinal neovascularization is poor. The incidence of retinal detachment is higher in myopic eyes.

12.5Retinal Dystrophies

12.5.1Macular Dystrophies

Definition

Macular dystrophies are disorders of the macula that usually occur bilaterally and manifest themselves between the ages of 10 and 30.

12.5.1.1 Stargardt’s Disease

Definition

This is a macular dystrophy that proceeds from the retinal pigment epithelium.

Inheritance: Autosomal recessive disorder. Epidemiology: Stargardt’s disease is rare.

Symptoms: Progressive loss of visual acuity occurs between the ages of 10 and 20 years.

Findings and diagnostic considerations: Initial findings are slight with white “fleck” lesions in the macular region (Fig. 12.29), which may occur in combination with lesions in the entire fundus (fundus flavimaculatus). The electroretinogram and electro-oculogram will be normal or reduced. In the later stage, the white lesions significantly increase in size and number. This will not necessarily be reflected in the ERG or EOG.

Differential diagnosis: Other disorders involving white “fleck” lesions such as inherited autosomal dominant drusen must by excluded by ophthalmoscopy. The diagnosis is confirmed by fluorescein angiography. Blockage of the choroidal fluorescein is a characteristic feature of Stargardt’s disease.

Treatment: No treatment is available. Edge-filtered eyeglasses and magnifying near vision aids can help make better use of the patient’s remaining vision.

12.5 Retinal Dystrophies 341

Stargardt’s disease.

Fig. 12.29 Typical “fleck” lesions of the retina (arrow) and extensive atrophy of the pigment epithelium in the macular region.

Prophylaxis: No prophylaxis is possible. Examination of siblings and genetic counseling are indicated.

Clinical course and prognosis: The disorder is chronically progressive. Vision in the final stages is usually 0.1 (20/200) or less.

12.5.1.2 Best’s Vitelliform Dystrophy

Epidemiology: The disorder is rare, with an incidence similar to Stargardt’s disease.

Inheritance: The disorder is inherited as an autosomal dominant trait with variable penetrance and expressivity. The gene locus is on chromosome 11 (11q13).

Symptoms: Clinical manifestation occurs between the ages of 5 and 15 years. Initially there is a subjectively slight decrease in visual acuity. In the later stages of the disorder, vision is reduced to about 20/200.

Findings and diagnostic considerations: A typical feature of this form of macular dystrophy is that visual acuity is negligibly diminished at the onset of the disorder. However, the morphologic findings are remarkable. Ophthalmoscopy will reveal yellowish round vitelliform lesions in the macular region (Fig. 12.30) that look like the yolk of a fried egg. (The Latin word vitellus means egg yolk.) Usually these lesions are bilateral and symmetrical, although eccentric lesions may also occur. Table 12.7 lists the various manifestations.

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Best’s vitelliform dystrophy.

Fig. 12.30 The yellow,

sharply demarcated lesion appears like the yolk of a fried egg.

Table 12.7 Stages of Best’s vitelliform dystrophy

The macular change resembling an egg yolk gave rise to the name vitelliform dystrophy.

Differential diagnosis: An unequivocal diagnosis can usually be made on the basis of the clinical picture alone. Sharply reduced or absent light response in the EOG and ERG confirms the presence of Best’s vitelliform dystrophy.

Treatment: The causes of the disorder cannot be treated.

Prophylaxis: Examination of siblings and genetic counseling are indicated.

Clinical course and prognosis: The prognosis is more favorable than for Stargardt’s disease. The disorder is chronically progressive. Visual acuity in the better eye usually remains about 20/40. Secondary loss of visual acuity can result from subretinal neovascularization.