Age-related macular degeneration: An eye disease with its onset usually after age 60 that can progressively destroy the macula, the central portion of the retina, impairing central vision. Age-related macular degeneration (AMD or ARMD) rarely causes blindness because only the center of vision is affected. However, injury to the macula in the center of the retina can impair the ability to see straight ahead clearly and make it difficult to read, drive, or perform other daily activities that require fine central vision.
The macula is in the center of the retina at the back of the eye. As we read, light is focused onto the macula where millions of cells change the light into nerve signals that travel to the brain and tell it what we are seeing. This is our central vision. With normal central vision, we are able to read, drive, and perform other activities that require fine, sharp, straight-ahead vision.
There are two types of AMD — the dry type and the far less frequent wet type. Neither type causes pain. An early symptom of wet AMD could be that straight lines appear wavy. This happens because blood vessels leak fluid under the macula. The fluid raises the macula from its normal place at the back of the eye and distorts vision. Another sign that a person may have wet AMD is rapid loss of central vision. This is different from dry AMD in which loss of central vision occurs slowly. In both dry and wet AMD, the person may also notice a blind spot. If any of these changes in vision is noticed, an ophthalmologist should be consulted without delay.
Supplements of zinc together with the antioxidants vitamin C, vitamin E and beta-carotene reportedly slow the progression of dry AMD. In people with intermediate-stage disease dry AMD, zinc reduced the risk of the disease progressing to the advanced stage by 11%, and the antioxidants reduced the risk by 10%. When the two were combined, the risk was reduced by 19%. The daily doses of the antioxidants used in this study were 500 milligrams of vitamin C, 400 milligrams of vitamin E and 15 milligrams of beta-carotene (a molecule the body converts to vitamin A). The daily dose of zinc was 80 milligrams with 2 milligrams of copper added to prevent copper deficiency sometimes associated with high zinc intake. These amounts are well above the usual levels recommended by the Food and Drug Administration (FDA).
Agenesis: Lack of development. For example, agenesis of a toe means the toe failed to form.
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