How well older people see in dim light is the strongest predictor of future blindness, according to a study by Greater Baltimore Medical Center?s Dr. Janet Sunness.
Unlike the better known “wet” macular degeneration ? caused by excess blood vessels in the retina ? patients with dry degeneration lose the light-receptive cells on the retina, causing spots in their vision that grow together over time.
“If you catch it at the earliest stages ? when people have 20/50 vision or better ? within two years, 40 percent or more lost three lines of vision” on a specialized eye chart,” Sunness said.
“Twenty-seven percent were legally blind within four years. That?s faster than the loss from diabetes, and that gets much more attention,” she said.
Sunness found that testing patients with a special filter that simulates low-lighting situations can predict who will suffer the greatest vision loss.
“People with good eyes lose two lines of vision. People with [advanced dry macular degeneration] lose on average 4.7 lines or are totally unable to read the chart,” Sunness said.
Sunness, director of Richard E. Hoover Rehabilitation Services for Low Vision and Blindness at Greater Baltimore Medical Center, is presenting results of the study Sunday at the American Academy of Ophthalmology Annual Conference in Las Vegas.
Since low-light vision is the first to be affected, the study suggests this low-light measure can be used as a way of screening drugs and other potential therapies for their success at treating geographic atrophy.
By age 75, almost 15 percent of people have this condition, according to the National Institutes of Health. The disease becomes increasingly prevalent for each decade patients live over 50.
Other than age, risk factors include family history and cigarette smoking.
