Your eyes depend on a small spot (the macula) in the central area of the retina at the back of the eye for perceiving sharp detail with straight-ahead vision. Light from the objects you view enter through the clear portion of the eye, passing through the pupil and lens where it is focused upon the light sensitive layer called the retina. Your central, or macular, vision is what allows you to see well enough to read, drive or perform other activities that require sharp vision. Although most of us have wide peripheral vision, it does not allow us to see detail as well as with central vision. To demonstrate the function of the macula, choose a word in the middle of one of the above sentences and focus exclusively upon that word. With your focus remaining upon that word, use your peripheral vision to see how many words on either side of it you can read clearly.

Most people cannot read more than one or two short words on either side of that point of focus.

AMD is an abbreviation for an eye disorder called age-related macular degeneration. AMD is painless, and its most common symptoms include blurry vision of pictures or type. Straight lines in your field of vision such as telephone poles and the sides of buildings may appear wavy. In more severe forms dark or empty spaces may block the center of your vision and in its most severe form, AMD can lead to total blindness. AMD is the leading cause of visual impairment in people 75 or older and it is the most common cause of new visual problems among those older than 65. Leaking blood vessels under the macula cause the "wet" type of AMD whereas the slow breakdown of the cells within the macula causes "dry" AMD. In some families, AMD is more common and it may also be associated with arteriosclerosis and eye trauma.

Some research has focused on age-related deposits, called drusen, that are similar in molecular composition to plaques and deposits in other age-related diseases such as Alzheimer's disease and atherosclerosis.

Having macular degeneration does not mean you will develop Alzheimer's disease.

Scientists have established a strong link between lutein, a carotenoid found in dark green leafy vegetables and a reduced occurrence of AMD. Carotenoids are powerful antioxidants that neutralize some damage forming molecules and it is thought that lutein protects the eye by blocking harmful blue light from reaching the back of the eye.

The diagnosis of AMD is made by inspecting the eye by using a special scope to examine the retina and macula. Also, an Amsler grid may be used to detect blind spots or wavy lines in vision. There are no definite treatments that prevent AMD but some researchers think maintaining healthy blood pressure, not smoking and wearing sunglasses that block out ultraviolet rays may help prevent AMD.

World Wide Web Resources

Macular Degeneration International

www.maculardegeneration.org

This is an especially comprehensive Web site that covers all aspects of macular degeneration in language the public can understand.

National Eye Institute

www.nei.nih.gov/publications/armd-p.htm

The National Eye Institute is affiliated with the National Institutes for Health, and provides a Web page designed to help people with age-related macular degeneration better understand the disease.

Dr. Scott Gibbs is a Cape Girardeau neurosurgeon and editor-in-chief of Mosby's Medical Surfari. You may e-mail questions to him at drgibbs@semissourian.com or write in care of the Southeast Missourian, P.O. Box 699, Cape Girardeau, Mo., 63702-0699.