By Isabel M. Estrada Portales

There is more to the Sun than meets the eye… and that's good!

In fact, the less the sun meets the eye the better. So, now that the sun is out and the summer is here… did you get your pair of sunglasses yet?

Sunglasses are not just a fashion statement; they are a much needed shield against those ultraviolet rays that can cause irreversible damage to the eye. Now doctors recommend sunglasses even for babies.

The scientific evidence is piling up: long-term exposure to invisible ultraviolet radiation can damage our eyes and lead to vision loss, at any age. July is UV Safety Month and eye doctors across the nation are urging Americans to protect their eyes and their children's eyes by wearing sunglasses and wide-brimmed hats.

According to the American Academy of Ophthalmology (AAO), "recent studies have shown that prolonged exposure to the sun's invisible, high energy ultraviolet rays without protection may cause eye conditions that can lead to vision loss, such as cataracts and age-related macular degeneration. During the summer months the level of ultraviolet radiation is three times greater than in the winter."

Sunglasses and a wide-brimmed hat are the best defense system for your eyes against sunlight and harmful UV rays. To be effective, both must be worn every time you're outside for prolonged periods of time, even when it's overcast.

Sunglasses shopping

Well, of course, they have to look good! But there may be a couple of more important factors to which you should pay attention when shopping for sunglasses. Brand name and high price tags won't cut it.

"The most important thing is to purchase sunglasses that block 99 to 100 percent of UV-A and UV-B rays," said Richard Bensinger, MD, a comprehensive ophthalmologist in Seattle, Washington. "Don't be misled by the color of the lens or the price tag dangling from the frame."

The AAO says the ability to block UV light is not dependent on the darkness of the lens. UV protection can come from adding chemicals to the lens material during manufacturing or from a chemical coating applied to the lens surface. And as for the cost, many $10 sunglasses provide equal or greater protection than a $100 pair. With expensive sunglasses, you're paying for style, frame quality and options such as scratch-resistant coatings, and not necessarily protective UV ray blocking ability.

However, research from the Columbia University Medical Center in New York shows that color may matter, and you should pick yellow or amber tinted lenses over blue-tinted ones.

"A sunglass should block UV light and reduce blue light. Blue light is reduced by a yellow-tinted glass. Yellow- and amber-tinted sunglasses filter out blue light, reducing the amount of blue light getting to your eye," said Dr. Janet Sparrow, professor of ophthalmic science at Columbia University Medical Center in New York.

What exactly UV rays do to the eyes?

Like your skin, your eyes never recover from UV exposure. Studies show that exposure to bright sunlight may increase the risk of developing cataracts and age-related macular degeneration, both leading causes of vision loss among older adults. UV exposure, wind and dust can also cause pterygia, benign growths on the eye's surface.

"UV light affects the eye because it contributes to the formation of cataracts, which are opacities or light scattering foci in the lens of eye," explains Dr. Sparrow. "In the presence of the natural human crystalline lens the retina is not affected by UV light because the human lens absorbs UV light, protecting the retina. Our retinas are exposed however, to light in the visible range - including blue light."

In addition to the damage caused by a lifetime of exposure to bright sun, you need to protect your eyes from acute damage caused by outings on very bright days. Excessive exposure to ultraviolet light reflected off sand, snow, water or pavement can damage the cornea, the eye's surface.

"Sun damage to eyes can occur anytime during the year, not just in the summertime," said Dr. Bensinger. "Although July is designated as UV Safety Month, you should protect your eyes from damage all year long."

Similar to sunburn on your skin, corneal ultraviolet injuries are painful, but usually heal quickly.

Take these steps to protect your eyes from the sun:

• Select sunglasses that block ultraviolet rays. Don't be deceived by color or cost. The ability to block UV light is not dependent on the darkness of the lens or the price tag.
• Make sure your sunglasses block 99 percent or 100 percent of UV rays and UV-B rays.
• Ideally, your sunglasses should wrap all the way around to your temples, so the sun's rays can't enter from the side.
• In addition to your sunglasses, wear a broad-rimmed hat to protect your eyes. Don't be fooled by a cloudy day. The sun's rays can pass through the haze and thin clouds.
• Even if you wear contacts with UV protection, remember your sunglasses.
• Sunglasses should be worn whenever outside and it's especially important to wear sunglasses in the early afternoon and in higher altitudes, where UV light is more intense.

Eye Openers

Loss of central vision with age may be linked to quality of dietary carbohydrates

Age-related macular degeneration (AMD) is one of the leading causes of vision loss in older adults and a person's risk may partly depend upon diet. When it comes to carbohydrates, quality rather than quantity may be more important, according to new research by Allen Taylor, PhD, director of the Laboratory for Nutrition and Vision Research at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University, and colleagues. Their findings were reported in the April 2006 issue of the American Journal of Clinical Nutrition.

"Women who consumed diets with a relatively high dietary glycemic index had greater risk of developing signs of early age-related macular degeneration when compared with women who consumed diets with a lower dietary glycemic index," says lead author Chung-Jung Chiu, DDS, PhD, scientist in the Laboratory for Nutrition and Vision Research at the HNRCA and an assistant professor at Tufts University School of Medicine. High total carbohydrate intake, however, did not significantly increase the risk factor for AMD.

"In other words, the types of carbohydrates being consumed were more important than the absolute amount," explains Taylor, senior author. A high-glycemic-index diet is one that is rich in high-glycemic-index foods, which are converted more rapidly to blood sugar in the body than are low-glycemic-index foods.

Impaired vision common in U.S.

Teenagers, people with diabetes, Hispanics, and people who are economically disadvantaged have higher rates of visual impairment and can most benefit from corrective lenses.

"This study found that most people who have a visual impairment could achieve good vision with proper eyeglasses or contact lenses," said Paul A. Sieving, M.D., Ph.D., director of vision research at National Institutes of Health (NIH). "So, if you have trouble seeing, you should get your eyes examined as soon as possible. It may be that corrective lenses will improve your vision. But, if you do have an eye disease, the sooner it is found, the more likely it is that treatment can help preserve your vision."

Individuals with impaired vision may be at increased risk of injuries and elderly persons are at increased risk of falls and fractures and depression, according to background information in the article.

The most common reason for impaired vision may be refractive error, a condition usually correctable with eyeglasses or contact lenses. Refractive error is when the shape of the eye does not bend light correctly, resulting in a blurred image. The prevalence of visual impairment in the U.S. has not been surveyed nationally in several decades.

"The provision of corrective lenses to those individuals in need will be an important public health endeavor with implications for safety and quality of life," the authors conclude.

Links

Vision 101
http://www.omhrc.gov/templates/browse.aspx?lvl=1&lvlID=4

Healthy Vision 2010
http://www.healthyvision2010.org/

Patient Handout
http://www.aao.org/patients/eyemd/upload/uv_handout.pdf

Diagram of the Eye
http://www.nei.nih.gov/health/eyediagram/

Cataract: What you should know
http://www.nei.nih.gov/health/cataract/cataract_facts.asp

Facts about the Cornea and Corneal Disease
http://www.nei.nih.gov/health/cornealdisease/

National Eye Institute
http://www.nei.nih.gov/index.asp