 e've found there is no safe dose of exposure
to the sun's ultraviolet B rays when it comes to the risk of cortical cataract,
which means people of all ages, races and both sexes should protect their
eyes from sunlight year-round, says Sheila West, Ph.D., professor of ophthalmology
at the Johns Hopkins Wilmer Eye Institute.
 Cataract, a clouding of the eyes'
clear lenses, occurs when proteins in the lens change their structure due
to UV-B light exposure and block light coming into the eye. Cortical cataracts
affect the front of the lens.
West is senior author of a report
on the study, published in the August 26 issue of Journal of the American
Medical Association. The study was supported by the National Institute on
Aging.
The finding comes several years after
the so-called "watermen's study," in which West and her colleagues
showed that crab fisherman working on Maryland's Chesapeake Bay had more
cortical cataract compared to people with less sunlight exposure. The current
finding shows that even the general public those who work indoors and only
get sunlight during leisure activities in the yard or on vacation may be
at increased risk for cortical cataract if precautions aren't taken.
The Hopkins study, conducted in Salisbury,
Md., determined the amount of UV-B exposure in 2,520 adults, age 64 to 84,
of whom 26.4 percent were African Americans. The Hopkins researchers photographed
the lenses of all participants and questioned them about their use of glasses,
sunglasses and hats during work and leisure activity, as well as the geographic
locations of these activities.
The team also used a special device
mounted on eyeglasses of over 250 participants to measure the amount of
UV-B light reaching their eyes. Then, using a "correction factor"
model developed by the National Aeronautics and Space Administration, the
researchers estimated exposure to UV-B the participants got when they traveled
to areas outside the Eastern Shore.
The results of the study are especially
important for children, according to West, because they have many years
of exposure ahead of them, and the effect of sunlight exposure appears to
be lifelong. "Kids get sunburned just like adults," West says.
"So there's no reason to think they are more resistant than adults
to lens damage from UV-B rays."
"Every time you go out into
the sun, your eyes can take a hit from UV-B rays," says West. "The
good news is it's never too late to start protecting your eyes, because
the lens change is probably from an accumulated dose over the years. That's
why everyone needs to get into the habit of protecting their eyes."
Even inexpensive, plastic sunglasses
are good absorbers of UV-B, according to West, and how dark the glasses
are isn't an issue, since any plastic eye wear will absorb the invisible
UV-B light. For children, however, the glasses should be shatterproof to
prevent eye injury in case of an accident. Dark glasses are needed to block
the visible light from the sun.
The researchers calculated there
is a 10 percent increase in risk for cataract for every 0.01 "Maryland
sun years" of exposure. A Maryland sun-year is the amount of UV-B that
falls in Maryland over one year. The eye receives anywhere from 9 percent
to 18 percent of this exposure.
Other authors of the study include
Donald D. Duncan, Beatriz Munoz, Gary S. Rubin, Linda P. Fried, Karen Bandeen-Roche,
and Oliver D. Schein. | 
