"Dry" AMD – Advances slowly, and may be hardly noticeable. Ninety percent of all people with AMD have this disorder. Exactly why it develops is not known, but it seems to be caused by aging and thinning of the tissues of the macula. A slow breakdown of the light-sensing cells in the macula leads to a gradual loss of central vision.
"Wet" AMD – Although only 10 percent of all people with AMD have this form, it accounts for 90 percent of all blindness from the disease. As dry AMD worsens, abnormal blood vessels may form underneath the retina. These new blood vessels tend to be very fragile, and will often leak blood and fluid. This causes damage to the overlying retinal tissue, and can lead to rapid and severe loss of central vision.