Researchers have a new clue about why some people lose their vision in old age and others do not. They have found genes that increase the risk a disease called macular degeneration will advance to blindness. As VOA's David McAlary tells us, macular degeneration is the leading cause of blindness in people over age 55.
Ten years ago, Harry Meyer began to notice his eyesight was fading. "I just realized that this old right eye was not doing what it should do," he said.
Harry's doctors found that he suffers from macular degeneration, the cause of vision loss in one of four people over age 75. The macula is part of the inner lining at the back of the eye called the retina, and it is responsible for central vision as opposed to peripheral or side vision. Degeneration means that the macula thins and in some cases bleeds.
But not everyone who has the disease loses vision, so researchers set out to learn why. They were led by physician Joanna Seddon at Tufts-New England Medical Center near Boston. "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," she said.
To determine which risk factors lead to vision loss, Seddon's group tracked almost 1,500 macular degeneration patients for six years. Their work included analyzing the volunteers' genes from blood samples and is reported in the Journal of the American Medical Association. "Common variations in two genes predict whether macular degeneration progresses to the advanced stages in visual loss," she said.
People with macular degeneration who had irregularities in either or both of two specific genes had 2 1/2 to 7 times the increased risk of vision loss compared to those whose genes were normal. They also found behavioral factors play a role, specifically smoking and being overweight. "If you had all the risk factors together, both genes plus being a smoker plus being obese, then all together that would increase your risk by 19-fold," Seddon said.
Seddon says she believes that identifying these genes will lead to new ways of treating and preventing macular degeneration.
A study on two monkeys shows that electrodes implanted in the brain might someday be a cure, not only for vision lost to macular disease, but also for other eye ailments.
According to a paper in the Proceedings of the U.S. National Academy of Sciences, Harvard Medical School researchers inserted the electrodes between the monkeys' retinas and a vision processing part of their brains. They say the animals interpreted an electrical stimulus as a point of light, judging by their eye movements.
The scientists plan to expand the experiments using more electrodes until the animals can see shapes. They hope eventually to perform the tests on people.