The Dark Eyes Have It -- a Higher Risk of Cataracts, That Is
WebMD News Archive
Oct. 5, 2000 -- More people are slathering on sunscreen now that it's a well-known fact that ultraviolet (UV) rays from the sun can cause damage to skin and lead to skin cancer. An Australian study serves as a reminder that the sun can affect other parts of the body as well. Researchers have discovered that people with brown or tan eyes may be more than twice as likely to develop cataracts than their blue-, green-, or hazel-eyed peers.
Researcher Robert Cumming, PhD, tells WebMD it's not just those who work outdoors or loll around on the beach without protection from the sun who are at increased risk for developing cataracts, but just everyday people. "According to our research, those with darker eyes are at greater risk, whether they're sun worshipers or not," says Cumming, a professor of community health at the University of Sydney.
The National Eye Institute -- a branch of the National Institutes of Health -- describes a cataract as a clouding of the eye's lens that causes a loss of vision. The lens of the eye is similar to the lens of a camera and handles the job of focusing images. As people age, cataracts develop when the proteins in the lens cloud up, blurring a small area. Over time, the cataract may grow larger and involve more of the lens, making it harder to see.
In the study -- which appeared in a recent edition of the American Journal of Ophthalmology --more than 3,500 people aged 49 to 97 were recruited in the early 90s.
The participants underwent a thorough eye exam. The researchers then gathered information about each person's lifestyle, such as cigarette smoking, diabetes, steroid use, and at what age distance glasses were first worn. They also examined sun-related skin damage, skin color, and noted each subject's eye color.
Researchers discovered that people with dark brown eyes were up to 2.5 times more likely to have a certain type of cataract and, to a lesser degree, more likely to get other types of cataracts.
Why? One theory is that darker eyes actually increase the risk of cataracts by absorbing light and increasing the temperature of the lens when exposed to the sun -- much like wearing black clothes in the summer. This specific question was not answered, but Cumming says, "Our research shows that while UV rays may increase the risk, dark-eyed people ... are at greater risk then their fair-eyed friends whether they're out in the sun or not."