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DURHAM, N.C. -- The National Eye Institute, part of the National Institutes of Health, has awarded a $2.2 million grant to support Duke University Medical Center's search for a gene that triggers macular degeneration, the leading cause of vision loss in older Americans.

"There's evidence that age-related macular degeneration (ARMD) has a genetic link, that it runs in families," said Dr. Monica De La Paz, primary investigator for Duke Eye Center's part in the five-year study. "Treatment options for the many elderly people with this condition are very limited, primarily because we do not know exactly what factors are important in causing the disease. The goal of this study is to determine whether there is an underlying gene -- or genes -- that predisposes people to develop ARMD. We also hope to find whether there is an interaction of environmental and genetic factors in development and progression of the disorder."

Duke's Margaret Pericak-Vance, a member of the team of neurology researchers responsible for locating apolipoprotein E (apo-E), a gene linked to Alzheimer's disease, will work with De La Paz to try to unravel the genetic puzzle. Dr. Johanna Seddon from Boston's Massachusetts Eye and Ear Infirmary and Jonathan Haines of Massachusetts General Hospital also are working on the problem.

ARMD is the most common cause of severe vision loss among American senior citizens. It affects the retina, the thin layer of tissue at the back of the eye that acts as a projection screen from which images are transmitted by nerves to the brain.

In the most common, or wet form of ARMD, blood vessels grow abnormally under the macula, the very center of the retina with the most sensitive photoreceptors and the part of the eye responsible for the sharpest vision. Leakage of blood or scarring from the abnormal vessel growth can destroy that sharp central vision, leaving patients with varying degrees of blurred central vision. In the less common dry form of ARMD, no new blood vessels grow, but there is slow, progressive vision loss due to degeneration of the macula.

Laser surgery, the only treatment currently approved for ARMD, can sometimes slow or stop the progression of the disorder, but only a small fraction of patients are candidates for laser treatment. Even with treatment, progressive vision loss frequently continues.

In the gene-mapping project at Duke and in Boston, researchers hope to discover how to identify people at risk of developing ARMD and to explore new ways of preventing the disorder. Analyzing the potential important genetic, environmental and biological factors associated with the disease may lead to the development of better treatment or preventive measures, De La Paz said.