Serous retinopathy, a cause of monocular visual disturbance in young or middle-aged males, may be associated with the use of corticosteroids. The entire perimacular zone is elevated by edema fluid. The condition may arise acutely or slowly. Metamorphopsia (distortion of vision) in one eye is a common presentation, but acuity is not much impaired. The optic disc remains normal. The retinal change (leakage of vascular fluid into the subretinal space) causes a loss of visualization of the detail of the choroid and is demonstrated by fluorescein angiography or by optical coherence tomography (OCT). The condition tends to resolve over several months and can be treated by laser to seal the sites of leakage.
Chorioretinitis, the result of an infectious process, may cause difficulty in diagnosis. Cat Scratch disease, caused by Bartonella henselae, is a consideration. In many patients the initial diagnosis had been retrobulbar neuritis. One cannot depend upon the appearance of a macular star (see earlier under “cotton wool patches”) for diagnosis.
A large number of patients with HIV-AIDS develop retinal lesions of various types. Infarcts of the nerve-fiber layer (cotton-wool patches), hemorrhages, and perivascular sheathing are the usual findings. Toxoplasmosis is the most common infective lesion, followed in frequency by cytomegalovirus (CMV), but histoplasmosis, Pneumocystis carinii, herpes zoster, syphilis, and tuberculosis are well documented. CMV may cause a particularly severe necrotizing retinitis and permanent impairment of vision. Both the retina and choroid may be involved by these diseases, in which case the ophthalmoscopic picture is characteristic, showing the destruction of the “punched-out” lesions that exposes the whitish sclera, and deposits of black pigment. The choroid may also be the site of viral and noninfective inflammatory reactions, often in association with painful recurrent iridocyclitis and lacrimal inflammation.
Degenerations of the retina are important causes of chronic progressive visual loss. The retinal degenerations assume several forms and can be associated with progressive conditions of the brain or other organs. The most frequent degeneration in youth and middle age is retinitis pigmentosa, a hereditary disease of the outer photoreceptor layer and subjacent pigment epithelium. The retina is thin, and there are fine deposits of black pigment in the shape of bone corpuscles, more in the periphery; later the optic discs become atrophic (described as “waxy pallor”). The disorder is marked by constriction of the visual fields with relative sparing of central vision (“gun-barrel” vision), metamorphopsia (distorted vision), delayed recovery from glare, and nyctalopia (reduced twilight vision). The causes of retinitis pigmentosa and related retinal degenerations are diverse, linked to deficits in more than 75 different genes. In one form of isolated retinitis pigmentosa, which follows an autosomal dominant pattern of inheritance, the gene for rhodopsin (a combination of vitamin A and the rod-cell protein opsin) produces a defective opsin, resulting in a diminution of rhodopsin, diminished response to light, and eventual degeneration of the rod cells (Dryja et al). Retinitis pigmentosa is associated with the