The macula is a tiny circle in the middle of the retina, a light-sensitive membrane that lines the inside of the back of the eye. In older people, it sometimes begins to deteriorate or degenerate for unknown reasons. Women are believed to be more at risk than men.
Macular degeneration affects more than 10 million persons in the United States and is the leading cause of legal blindness for those 55 years of age and older. However, macular degeneration rarely leaves you totally unable to see.
There are two types of this disease:
- Dry macular degeneration accounts for about 90% of cases. The tissue of the retina shrinks and pigments accumulate inside of it. Dry macular degeneration can progress to the wet form.
- In wet macular degeneration, new blood vessels grow around and behind the macula. There's sometimes bleeding in or behind the macula. Material seeps into the retina and settles in the macula. This is called exudate. Eventually the exudate disappears, but a scar takes its place. All people who have wet macular degeneration had dry macular degeneration first.
The causes of macular degeneration are unknown, but the risk grows with age. Because it's extremely rare in people under age 50, the condition is usually referred to as age-related macular degeneration (AMD).
There are some known risk factors for macular degeneration. Smoking may increase your chances of developing the condition and seems to speed up its progress. High cholesterol levels, high blood pressure, obesity, and a diet lacking in dark green leafy vegetables and omega-3 fatty acids may also be associated with macular degeneration. Women seem to be at a higher risk than men.
Macular degeneration runs in some families but not in all. Recent studies of twins suggest that both genes and environment contribute to the onset of macular problems. Wet macular degeneration, at least, seems to be more common in people with poor cardiovascular health. Although it only accounts for about 10% of the cases, wet macular degeneration is responsible for 90% of the blindness caused by this disease.