Genetic Link Found in Macular Degeneration
Posted April 24, 2007
Reseachers have found a genetic basis for determining how some people with macular degeneration, the leading cause of blindness in people over age 55, are able to retain some of their eyesight.
The macula is part of the retina that provides central vision. When it deteriorates, a growing dark spot impairs vision.
About one-quarter of people over age 75 lose their vision because of macular degeneration. But not everyone with the disease loses vision.
A study of about 1,500 patients over six years revealed risk factors that lead to actual vision loss. The results appear in the new Journal of the American Medical Association.
"We studied whether genetic and environmental factors are related to whether someone with this eye disease progresses to where they can no longer see other people's faces," said Dr. Johanna Seddon of the Tufts New England Medical Center. "Common variations in two genes predict whether macular degeneration progresses to the advanced stages in visual loss."
The risk of vision loss increases seven-fold if one or both of the genes has an abnormality. If someone has other risk factors, such as smoking or being overweight, on top of the gene abnormality, their risk increases 19 times.
Harry Meyer, who learned 10 years ago that he had macular degeneration, has never smoked and isn't overweight. But his grandfather lost his vision as he aged.
Medical treatment, good nutrition and exercise has preserved much of Meyer's vision.
"I can still read newsprint in the newspaper, and that's my main measure of success," he said.
Seddon said she believes identifying the genes linked to macular degeneration will eventually lead to new ways of treating and preventing the disease. But that might be many years away, she said.