Age related macular degeneration is one of the leading causes of blindness in the United States. It is a medical condition which affects older adults that results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in "dry" and "wet" forms. It is a major cause of visual impairment in older adults over 50 years of age. Macular degeneration can make it difficult to read or recognize faces, although enough peripheral vision remains to allow other daily activities. Although some degeneration affecting younger individuals are sometimes referred to as macular degeneration, the term generally refers to age-related macular degeneration (AMD or ARMD).
The inner layer of the eye is the retina, which contains nerves that communicate sight, and behind the retina is the choroid which contains the blood supply to the macula. The macula is made up of millions of light-sensing cells that collectively produce central vision. AMD occurs in two forms.
"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.