CHICAGO -- More than 28 million Americans over age 40 have eye ailments that put them at risk for vision loss and blindness, researchers say, warning that the numbers will surge as the population ages.
Cataracts are the leading cause of blindness worldwide and the leading cause of poor vision in the United States, affecting an estimated 20.5 million American adults. That number is expected to climb to 30.1 million in the next 20 years, researchers say.
Other major causes of blindness and vision loss are macular degeneration, glaucoma, and diabetic retinopathy. All are strongly linked with aging.
The figures published yesterday in April's Archives of Ophthalmology present the most accurate estimates to date on the prevalence of major causes of blindness and visual impairment in the United States, according to Dr. Frederick Ferris III of the National Eye Institute, which helped fund the research.
The data are crucial for showing where research dollars need to be spent to avoid a "tidal wave of chronic ocular disease over the next few decades," Ferris and Johns Hopkins University researcher James Tielsch wrote in an accompanying editorial.
Currently, 1 million Americans over 40 are blind. They are among 3.3 million who suffer from some vision loss, a number projected to reach 5.5 million by 2020.
The numbers are of concern not just because of their magnitude, but also "because of the substantial increases in health care costs they spell," said Dr. Nathan Congdon, a coordinator of the research and an associate professor of ophthalmology at Johns Hopkins.
More than $3 billion yearly is spent on cataract treatment alone, which usually involves surgery, Congdon said. Cataracts are cloudy areas that develop on the eye's lens and can result from injuries or age-related chemical changes.
Macular degeneration involves damage to the macula, the center of the retina at the back of the eye. About 1.8 million adults are affected, the researchers said. In some cases, light-sensitive cells in the macula break down, gradually impairing vision.
In others, leaky new blood vessels form behind the retina and cause vision loss.
Treatments include lasers or laser-activated drugs, and recent studies have shown that high doses of antioxidant vitamins can help slow or even prevent vision loss in macular degeneration.
Glaucoma affects about 2.2 million US adults. It usually involves a buildup of fluid that normally bathes the eye, causing pressure that damages the optic nerve. Treatment includes eye drops and surgery.
Diabetic retinopathy, which involves eye damage resulting from blood vessels weakened by diabetes, affects about 4 million American adults. Laser therapy, surgery and better control of diabetes are among the treatments.