Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Macular Degeneration

What Is It?

Macular degeneration is a common cause of blindness and vision problems among people older than 50 in the United States. This condition also is called age-related macular degeneration, or AMD. AMD damages the macula, a small part of the eye's light-sensitive retina, the layer of tissue that sends vision signals to the brain. Because the macula is responsible for seeing sharp details directly in the center of the field of vision, damage caused by AMD can interfere with:

• The ability to see straight ahead, necessary for driving and viewing distances, such as when recognizing faces or watching television

• Fine, detailed vision, necessary for reading newsprint, sewing, working with crafts and making repairs

Most people with AMD have fluffy, yellow-white spots on the macula. These spots are called drusen. Not everyone who gets AMD has these spots, and the connection between drusen and AMD is not clear. There are two ways to lose vision as a result of AMD. Both occur during the early stage of the disorder.

• Dry (nonneovascular) AMD — About 90% of people who lose significant vision from AMD have this form of the illness. In dry AMD, the layer of cells under the retina stops functioning well, causing the light-sensing cells that overlie this area to dysfunction or disappear over time, producing blank spots in an eye's central vision that are subtle at first then more noticeable later.

• Wet (neovascular) AMD — In wet AMD, delicate new blood vessels begin to grow beneath the retina and can leak blood and fluid into the macula, causing scarring. Damage from the blood vessels, blood and fluid, and scar tissue can occur in a very short period of time, causing rapid loss of vision over days to weeks and continued loss of vision over time. This is probably responsible for about 90% of the cases in which AMD has led to legal blindness. But it is less common than the dry form./DCB

Age is the most important risk factor for AMD, and the early stage () currently affects approximately 3.5 million to 10 million people in the United States older than 65. The exact number depends on how macular degeneration/DCB is defined. Only a small percentage of people in their 50s have AMD. This percentage increases dramatically in people aged 75 and older. In that age group, about 10% have the advanced form of AMD that causes vision loss. AMD also may be slightly more common in women and in those with a family history of AMD. Caucasians may be at greater risk of developing the wet form. Cigarette smoking and risk factors for cardiovascular disease, such as high levels of blood cholesterol, may be additional risk factors for AMD.