Age-Related Macular Degeneration

Age-related macular degeneration (AMD; maculopathy) is a degenerative disorder of the macula. AMD is a common cause of worsening central vision in the elderly. Diagnosis is by funduscopy; fluorescein angiography helps direct treatment. Treatment is with photodynamic therapy, laser photocoagulation (in specific cases), intravitreal injection of vascular endothelial growth factor inhibitors (eg, pegaptanib) for neovascular AMD, and vision aids.

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss and legal blindness in the elderly. AMD is more common among whites than among blacks. Smoking is a risk factor. In addition, AMD may be hereditary; risk may be linked to variations in the complement factor H gene on chromosome 1q31. The role of cardiovascular disorders, hypertension, ultraviolet light, diet, and cholesterol levels is unclear.

AMD has 2 forms. In atrophic AMD (dry form), often called geographic atrophy, the retinal pigment epithelium disintegrates and overlying photoreceptor cells are lost, causing irregular pigmentation of the macular area but no elevated macular scar and no hemorrhage or exudation in the macular area. The dry form reduces vision but usually only to levels of 20/50 to 20/400.

In exudative AMD (wet or neovascular form), which is much less common (10% of total cases), a subretinal network of new blood vessels (called choroidal neovascularization) forms. These vessels may leak fluid or bleed beneath the retinal pigment epithelium and between the retinal pigment epithelium and sensory retina. Fluid accumulation or hemorrhage may cause localized elevation of a macular area or pigment epithelial detachment. Subsequent fibrous scarring disrupts the flow of nourishment to photoreceptor cells and causes their death, resulting in loss of central visual acuity. Eventually, an elevated scar forms at the posterior pole. The wet form accounts for most cases of blindness (visual acuity of <= 20/200) caused by AMD.

Symptoms and Signs

Both forms of AMD are often bilateral.

In atrophic AMD, central visual acuity is lost slowly and painlessly. Central scotomas (blind spots) usually develop early. Reduction of vision is mild to moderate, leading to blindness in about 15% of patients.

In exudative AMD, rapid vision loss is typical. Although peripheral vision and color vision are usually unaffected, patients may become legally blind in the affected eye or eyes. The first symptom is distortion of central vision in one eye; objects appear larger or smaller or straight lines appear distorted, bent, or without a central segment.

Drusen develop early. They are outgrowths of the basement membrane of the retinal pigment epithelium that protrude into the cells, causing them to bulge anteriorly. Through an ophthalmoscope, drusen appear as small, rounded, yellow-white areas with indistinct borders.

If central vision is distorted in only one eye, patients may not notice any change in vision. However, if they view a fine-lined (Amsler) grid with each eye alternately, distortion can be quickly detected. Therefore, patients considered at high risk of age-related macular degeneration are given such a grid to view each morning. These patients include those with many drusen, especially if drusen are confluent, and those with macular degeneration in one eye.

After distortion occurs, visual acuity may decrease, possibly within days. If distortion occurs, patients should see an ophthalmologist immediately. The presence of large drusen, irregular macular pigmentation, or advanced unilateral AMD increases the risk of advanced disease.

Diagnosis

AMD is diagnosed based on the clinical appearance of the retina. Funduscopy shows pigmentary or hemorrhagic disturbance in the macular area of the affected eye; some pigmentary disturbance and drusen are almost always seen in the macula of the contralateral eye. Other findings may include retinal detachment, lipid exudates, tissue atrophy, and macular scarring.

Angiography should be done when funduscopic findings suggest neovascularization; such findings include subretinal hemorrhage, localized retinal elevation, retinal edema, and gray discoloration of the subretinal space. Fluorescein angiography shows and characterizes a subretinal choroidal neovascular membrane.

Treatment

Without treatment, exudative AMD results in substantial vision loss and often in blindness. Results of treatment depend on the size, location, and type of neovascularization. Thermal laser photocoagulation of new blood vessels outside the fovea may prevent severe vision loss. Photodynamic therapy is beneficial for certain types of neovascular membranes; a photosensitizing dye (verteporfin) is injected IV just before treatment with a cool photoactivating light. Intravitreal injection of a vascular endothelial growth factor inhibitor (eg, pegaptanib) halts the rate of vision loss in patients with exudative AMD. Other treatments under evaluation include transpupillary thermotherapy, subretinal surgery, and macular translocation surgery.

Patients who have lost central vision may benefit from vision aids (eg, magnifiers, high-power reading glasses, computer monitors that scan text and read it out loud, telescopic lenses, talking clocks, implanted telescopes). Counseling by therapists who specialize in low vision is advised. Patients who smoke are advised to stop.

Prevention

No preventive treatment has proved effective for AMD, but patients at risk of advanced disease 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. Beta carotene can cause anemia, prostatic hypertrophy, stress incontinence, and, in smokers, an increased risk of lung cancer.

This topic was last updated May 2006.