There are two types of macular degeneration. About 90 percent of people with macular degeneration have what's known as the "dry" type, and the remaining 10 percent have the "wet" type. However, the wet type accounts for 90 percent of all blindness from the disease.
In wet macular degeneration, new blood vessels grow. Because these new blood vessels tend to be very fragile, they will often leak blood and fluid under the macula. This causes rapid damage to the macula, which can lead to the loss of central vision in a short period of time.
In dry macular degeneration, the light-sensitive vision cells deteriorate, but there is no bleeding. Scientists are still not sure what causes dry macular degeneration. Studies suggest that an area of the retina becomes diseased, leading to the slow breakdown of the light-sensing cells in the macula and a gradual loss of central vision.
(Click Types of Macular Degeneration for more information.)
No one knows exactly what causes macular degeneration, and doctors can seldom explain why one person gets it and another does not. However, research has shown that people with certain risk factors are more likely than others to develop macular degeneration. A risk factor is anything that increases a person's chance of developing a disease.
Specific risk factors of macular degeneration include:
- Family history
- Low lifetime intake of green, leafy vegetables
- High blood pressure
- Cardiovascular disease.
(Click Causes of Macular Degeneration for more information.)