AMD

By Peter Galvin, MD

If, like me, you watch the evening news on TV, then you are inundated daily with ads for medical conditions like age-related macular degeneration (AMD). AMD is a condition that can cause severe vision impairment in older adults. It affects about 20 million Americans and 196 million people worldwide. Although it does not typically cause complete vision loss, it accounts for 6% to 9% of legal blindness globally. Those with late-stage AMD may lose the ability to read, drive, and recognize faces.

AMD affects the macula, which is the central part of the retina, or back of the eye. The retina is responsible for creating visual images. Those with AMD develop deposits of lipid, mineral, and protein called drusen beneath the retina. As drusen enlarge, AMD progresses from early to intermediate stage. Late-stage AMD has two forms:

• Geographic atrophy, also known as dry AMD. This is the most common form of AMD and results from progressive atrophy of the macula that results in a slow decline of central vision.
• Neovascular atrophy, also known as wet AMD. In this form, abnormal blood vessels in the macular region may bleed and cause rapid worsening of vision.

Early-stage AMD is usually asymptomatic, meaning that those with it are not aware they have it. This is why, especially for those 55 years and older, regular eye exams are crucial. With intermediate-stage AMD, individuals may have difficulty seeing in low-light, low-contrast settings (like reading a menu in a dimly lit restaurant), and vision may become blurry or distorted. Age is a major risk factor, which increases significantly at about age 55 years. Cigarette smoking is a strong risk factor, and genetic factors account for about 70% of the risk of developing AMD.

Eye care professionals diagnose AMD by dilating the pupil and examining the retina using an instrument called a slit lamp, which focuses light directly on the retina. Also used are ocular coherence tomography (OCT) scans that provide high-resolution images of the retina which determine the stage of AMD and can magnify drusen, identify other age-related retinal changes, and can reveal leaky blood vessels. OCT scans help monitor progression of AMD and can determine response to treatment. Treatment recommendations depend on disease stage, however common advice includes smoking cessation, physical activity, and a healthy diet that includes fruits, vegetables, and fatty fish. Also recommended are the use of daily antioxidant vitamins and minerals that include vitamin C, vitamin E, carotenoids, and zinc. Those with wet AMD are treated with repeated eye injections of anti-vascular endothelial growth factor, which blocks new blood vessel growth in the macula and can improve or stabilize many individuals with wet AMD.

For more information go to the National Eye Institute at: www.nei.nih.gov

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