An Introduction to Macular Degeneration
Age-related macular degeneration (AMD, or just macular degeneration) is a common eye disease associated with aging. It blurs the sharp, central vision you need for "straight-ahead" activities, such as reading, sewing, and driving. In some people, macular degeneration advances so slowly that it has little effect on their vision as they age. But in others, the disease progresses faster and may lead to a loss of vision in one or both eyes.
About 1.7 million Americans have some form of macular degeneration. Macular degeneration is the leading cause of vision loss among Americans ages 65 and over.
In order to understand macular degeneration, it is helpful to understand the parts of your eye involved with sight. These structures include the cornea, iris, pupil, lens, macula, and retina.
Your cornea is a thin, clear layer on the outside of your eye. The iris, or the colored part of your eye, is a muscle that controls the amount of light going through your pupil, which is the round opening in the center of your eye. Behind the iris sits the lens, which is just larger than your pupil. The iris is enclosed by a thin, clear capsule that holds the lens in its proper place.
When light enters your eye, the cornea and lens form the light rays into a beam of light that is focused directly onto your retina -- the light-sensitive tissue at the back of the eye. The retina instantly converts light, or an image, into electrical impulses. The retina then sends these impulses, or nerve signals, to the brain through the optic nerve. The optic nerve is a bundle of more than one million nerve fibers connecting the retina to the brain.
The macula is located in the center of the retina. It is made up of millions of light-sensing cells that help to produce central vision.
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