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Age-related
macular degeneration is atrophy or degeneration of the macula. It
is a common cause of worsening central vision in elderly patients.
Funduscopic findings are diagnostic; fluorescein angiography assists
in directing treatment. Treatment is with laser photocoagulation and
low-vision devices.
Etiology
and Pathophysiology
Age-related macular degeneration (AMD) is a leading cause of vision loss in the elderly. It is more common in whites than in blacks. No predisposing systemic risk factor is known, but AMD may be hereditary; an association between smoking and AMD has been shown. The role of cardiovascular disease, hypertension, and cholesterol levels remains unclear.
Two different forms occur: In atrophic AMD (dry form), often referred to as geographic atrophy, there is irregular pigmentation of the macular region but no elevated macular scar and no hemorrhage or exudation in the macular region. In exudative AMD (wet or neovascular form), which is much less common, a subretinal network of choroidal neovascularization forms. This network is often associated with hyperpigmentation of the macula and soft drusen. A localized elevation of an area of the macula or a pigment epithelial detachment may be caused by hemorrhage or fluid accumulation. Eventually, this network leaves an elevated scar at the posterior pole.
Ninety percent of the blindness caused by AMD occurs in the 10% of cases that have the exudative form.
Symptoms,
Signs, and Diagnosis
Both forms of AMD are often bilateral and are preceded by development of drusen (small yellow deposits that form under the macula). In atrophic AMD, central visual acuity is lost slowly and painlessly. Rapid vision loss is more typical of exudative AMD. Although peripheral vision and color vision are generally unaffected, the patient may become legally blind (< 20/200 vision) in the affected eye(s). The first symptom of exudative AMD is visual distortion in one eye, which can be detected with an Amsler grid (see Approach to the Ophthalmologic Patient: Visual field testing). Central blind spots (scotomas) usually develop early in atrophic AMD. Funduscopy reveals pigmentary or hemorrhagic disturbance in the macular region of the involved eye; the contralateral eye almost always shows some pigmentary disturbance and drusen in the macula. Other findings may include retinal detachment, lipid exudates, tissue atrophy, and macular scarring.
AMD is diagnosed by clinical appearance of the retina. Fluorescein angiography may reveal a neovascular membrane beneath the retina. An angiogram is obtained when findings suggestive of neovascularization are present; such findings include subretinal hemorrhage, localized retinal elevation, retinal edema, and gray discoloration of the subretinal space. Fluorescein angiography demonstrates and characterizes a subretinal choroidal neovascular membrane.
Prognosis
and Treatment
Atrophic AMD produces mild to moderate reduction of vision but rarely leads to blindness. There is no recommended treatment, but patients at risk of advanced disease (eg, those with large drusen or irregular macular pigmentation) may benefit from daily supplements of zinc oxide 80 mg with copper 2 mg, vitamin C 500 mg, vitamin E 400 IU, and beta carotene 15 mg. β-carotene can cause anemia, prostatic hypertrophy, stress incontinence, and, in smokers, an increased risk of lung cancer.
If exudative AMD is untreated, vision typically deteriorates substantially, often to blindness. However, peripheral vision is usually retained. Results of treatment depend on the size, location, and type of neovascularization. Thermal laser photocoagulation of neovascularization outside the fovea may prevent severe vision loss. Photodynamic therapy, a laser treatment, provides benefit under specific circumstances. Pegaptanib is a new injectable selective vascular endothelial growth factor antagonist that can be used for the treatment of neovascular AMD. Other treatments being evaluated include transpupillary thermotherapy, subretinal surgery, and macular translocation surgery.
For patients who have lost central vision, low-vision devices, such as magnifiers, high-power reading glasses, computer monitors, and telescopic lenses, are available. Low-vision counseling is advised.
Last full review/revision November 2005
Content last modified November 2005
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