Age-Related Macular Degeneration (AMD)

Age-related macular degeneration is a retinal degenerative disease that causes a progressive loss of central vision. AMD is the most common cause of blindness and vision impairment in Americans aged 60 and older. There are two types of AMD: dry (earlier stage) and wet (later stage).

Dry AMD accounts for about 90 percent of all cases, and normally affects vision less than wet AMD. Dry AMD is sometimes called atrophic, nonexudative, or drusenoid macular degeneration. A characteristic of dry AMD is the accumulation of tiny protein and fat-containing "drusen" deposits in a thin layer of cells beneath the photoreceptors in the retina called Bruch's membrane. The origin of drusen is unknown, but they may be from waste products of various cells and tissues of the retina. Drusen may interfere with the health of the macula, causing progressive degeneration of the photoreceptor cells. Drusen deposits can, however, be present without vision loss. The most severe form of dry AMD is called geographic atrophy, which may cause significant vision loss.

Geographic atrophy may be considered the end stage of dry AMD, causing severe vision loss. Over time, sometimes over many years, the atrophy of the RPE cells (due to drusen deposits in the retina) gets more prevalent with all of the macula being affected. Geographic atrophy looks like a circle or spot of degeneration, right in the center.

Wet AMD accounts for about 10 percent of all cases of macular degeneration. Wet AMD is also called choroidal neovascularization (CNV), subretinal neovascularization, or exudative or disciform degeneration. In wet AMD, abnormal blood vessels grow beneath the macula. These vessels leak blood and fluid into the macula that damage photoreceptor cells. Wet AMD often progresses rapidly and can cause substantial loss of central vision.

Excellent progress is being made in understanding, predicting, and treating wet AMD, including the blood vessel growth blocking drugs Lucentis^®, Macugen^®, Visudyne^® , and Verteporforin^®. Numerous clinical research trials are being conducted to evaluate other promising treatments for wet AMD.

The Age-Related Eye Disease Study (AREDS), conducted by the National Eye Institute, revealed that a dietary supplement containing a combination of vitamins and minerals could help reduce the risk of advanced wet AMD and vision loss in people who are at greatest risk. Currently, a second NEI nutritional clinical trial, called AREDS II, is evaluating a modified version of the above supplementation, including addition of lutein, zeaxanthein, and/or omega-3 fatty acids.

For descriptions of juvenile forms of macular degeneration, see Best Disease, Stargardt Disease.