Age related macular degeneration (AMD) is a disease of the central retina (macula). This area is 3 mm in diameter. The central area of the macula is referred to as the fovea, a 0.5 mm diameter area which is crucial to our central vision. Patients with the disease gradually develop a gray spot (scotoma) in the center of their vision which gradually becomes larger and more dense, although the density may not be uniform. This can interfere with or prevent reading, driving or recognizing other people. Macular degeneration is not considered a "blinding" disease because with very few exceptions peripheral vision is maintained and individuals are able to get around quite well.

The condition generally starts as mild "dry" (non-exudative) AMD which can progress to more severe forms in 10 to 25% over five years. Of these more severe forms, 10% can progress to the "wet" (exudative) form in five years. In patients that have the "wet" form in one eye and the "dry" form in the other, depending upon the severity of the dry form present, the fellow eye can progress to the "wet" form in 5 to 87% in five years.

What do these terms "dry" and "wet" mean? Generally "dry" is less severe and "wet" is more severe. In the "dry" form, the ophthalmologist sees pigmentary changes and yellow deposits under the macula (drusen). In the "wet" form, fluid starts to build up under the retina often forming a blister under the retina and shortly thereafter bleeding from an abnormal blood vessel under the retina (subretinal neovascular membrane) occurs into that blister which will lead to the destruction of the macula itself.

Present research into techniques of treatment are focusing on the more severe "wet" form in an effort to destroy the abnormal blood vessel and prevent bleeding. With the exception of the CAPT Study, no potential treatment for the "dry" form is in sight.