The retina's central portion, known as the macula, is responsible for focusing central vision in the eye, and it controls our ability to read, drive a car, and see objects in fine detail. Macular degeneration is caused by degenerative changes in this central portion of the retina. As people age, their chances for developing such degenerative eye diseases increase rapidly.
Unfortunately, the specific factors that cause macular degeneration are not conclusively known.
There are two basic types of macular degeneration: "dry" and "wet." Approximately 85% to 90% of the cases of macular degeneration are the "dry" (atrophic) type. In the "dry" type of macular degeneration, the deterioration of the retina is associated with the formation of small yellow deposits, known as drusen, under the macula. This phenomena leads to a thinning and drying out of the macula. The amount of central vision loss is directly related to the location and amount of retinal thinning caused by the drusen. This form of macular degeneration is much more common than the "wet" type of macular degeneration and it tends to progress more slowly than the "wet" type. However, a certain percentage of the "dry" type of macular degeneration turns to "wet" with the passage of time. There is no known treatment or cure for the "dry" type of macular degeneration.
In the "wet" type of macular degeneration, abnormal blood vessels grow under the retina and macula. These new blood vessels may then bleed and leak fluid, thereby causing the macula to bulge or lift up, thus distorting or destroying central vision. Under these circumstances, vision loss may be rapid and severe. Many doctors recommend that immediate laser surgery is necessary in the early stages of "wet" macular degeneration if vision is to be saved. However, laser surgery does not guarantee that vision will be saved. Existing laser therapies are limited in their effectiveness and may also lead to scarring of the macula and additional vision loss.