Low vision -- poor eyesight that can't be corrected by glasses, contact lenses, surgery or medication -- afflicts more than 2 million Americans, according to the National Eye Institute (NEI). But this is a conservative estimate. Some 14 million Americans suffer from visual impairment if you include those with eye problems that hamper the performance and enjoyment of everyday activities. While among the elderly, the problem has many possible causes -- among them, diabetic retinopathy, retinitis pigmentosa, glaucoma and cataracts -- age-related macular degeneration (AMD) is the single greatest culprit. The specific causes of AMD, marked by abnormal cell development in the macula, the central part of the retina, are not known.

Age, however, is the biggest risk factor. The prevalence of AMD increases almost fourfold between the ages of 49 and 80, according to the National Eye Institute. Women, smokers and people with a family history of AMD are at higher risk. People with high cholesterol levels may also face a greater risk for developing the so-called wet form of the disease.

Because the condition affects central but not peripheral vision, AMD patients rarely become totally blind. But enough vision may be lost to require major changes in their lifestyle and routines.

Neither the wet nor the dry form of the disease causes any pain. The most common symptom of dry AMD is blurred vision and difficulty with reading. Some people find they need more light to read, and must be close in order to recognize faces or read street signs. As cells in the macula cease working, some people experience blurred spots in their central vision. Many people are unaware they have a problem as long as it is confined to one eye. If the second eye starts to deteriorate, the effects are more evident.

Early diagnosis may give patients more options for treatment. A doctor will look for drusen, tiny yellow deposits in the retina, and may ask the patient to look at an Amsler Grid, a patterned chart that looks like graph paper or a checkerboard. Seeing straight lines as wavy or blank spots on the grid often signals a problem. Distortions occur in AMD because the abnormal blood vessels raise the macula from its normal position.

There is no treatment for dry AMD, but since it tends to develop slowly, it doesn't usually cause drastic vision loss until the late stages.

Vitamin and mineral supplements may help some patients -- though perhaps more modestly than some product advertising suggests. In 2003 the Food and Drug Administration ordered one company, the Vision Group of North Hampton, New Hampshire, to stop advertising its product, Precision Vision, as a way to reduce the risk of degenerative eye disease. Owner James Parker said sales of the product have since been halted.

Other supplement companies have also stepped up their marketing since an NEI study released in 2001 found that over a six-year period, patients at high risk of developing advanced AMD who took large doses of antioxidant vitamins and minerals reduced their chances of getting the disorder by 25 percent. Principal investigator Emily Chew, deputy director of NEI's division of epidemiology and clinical research, says supplements should not be taken as a preventive measure or without consultation with an eye care professional.

Laser surgery to cauterize leaking blood vessels was the first procedure used to control wet AMD and is a treatment still used today. There are risks -- if the leaky vessels are in the center of the macula, the laser may scar or destroy some retinal tissue.

In a more recent approach known as photodynamic therapy, patients take a light-sensitive drug that enables the vessels to respond to a milder, less damaging laser. Repeat treatments are often necessary, but still may not help all patients. Some retinologists use lasers on small feeder vessels, trying to cut off the supply of extra blood to the larger central vessels. Other researchers are assessing the impact of drugs such as rhuFab, an antibody designed to stop the growth of new blood vessels in patients with moderate wet AMD.

Clinical trials are also underway to assess the effect of implanting miniature telescopes into the eyes of AMD patients. This would create an internal magnifier for distance viewing and reading but could also interfere with peripheral vision.

Since many of these treatments are still in their experimental stages, people with AMD should discuss them with their doctors. But don't expect miracle cures -- not just yet, anyway.

-- Elinor Waters is a counselor living in Washington, D.C.

References

First published December 18, 2003
Last updated February 19, 2008
Copyright © 2003 Consumer Health Interactive

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