Are There Different Forms Of Macular Degeneration?

Yes. Some rare kinds of macular degeneration occur in children. Called juvenile macular degeneration, they are hereditary diseases caused by abnormal genes passed from parents to their children. Macular damage can result from injuries to the eye, exposure to intense light, and infections. People with severe myopia, or nearsightedness, may develop macular degeneration. Macular damage can occur as a complication of diabetes and certain other diseases.

Most cases of macular degeneration, however, are age-related. AMD occurs in two forms, a "dry" form and a "wet" form. Both are painless. Wet AMD also is called neovascular macular degeneration because it involves growth of new blood vessels. "Neo-" means "new" and "vascular" means blood vessels. Dry AMD is called the non-neovascular form of AMD because it does not involve growth of new blood vessels.

• Dry AMD. About 90 per cent of people with AMD have the dry form. It involves a slow breakdown of light-sensitive cells in the retina and a gradual loss of central vision. Dry AMD may progress into the more serious "wet" form.

• Wet AMD. Although only 10 per cent of the people with AMD have the wet form, it causes 90 per cent of the blindness from AMD. In wet AMD, abnormal new blood vessels grow under the macula. The vessels have unusually delicate walls, and may begin to ooze blood and fluid. The fluid damages nearby light-sensitive retina cells. If the leaks continue, all of the cells in the macula may be injured within a few weeks.