FRIDAY, Aug. 20 (HealthDay News) -- Folks have been taught to slather on sunscreen, slip on a shirt and clap a hat on their heads to protect their skin from the sun's harmful ultraviolet rays.

That's all good. But not adding a pair of good sunglasses to the ensemble still leaves people at risk, eye doctors say.

Ultraviolet, or UV, rays can cause significant damage to unprotected eyes, resulting in a number of illnesses and disorders that can rob people of their sight.

"People are more aware of skin cancer. There's more awareness of exposing your skin to the sun," said Dr. J. Alberto Martinez, a practicing ophthalmologist in Bethesda, Md., and a clinical professor of ophthalmology at Georgetown University Medical School. "But at the same time, the eyes suffer dramatically from ultraviolet exposure. UV exposure is a public health problem, and, as an ophthalmologist, I see the continuous, serious problems that are caused by UV."

Both short- and long-term exposure to UV rays can cause vision problems and eye damage, according to the U.S. Environmental Protection Agency's Office of Air and Radiation.

People exposed to bright sunlight for even short periods can develop a "sunburn of the eye" in the form of either photokeratitis or photoconjunctivitis.

Photokeratitis is an inflammation of the cornea, the transparent front part of the eye that covers the iris, pupil and lens, according to the World Health Organization. "The sun can cause superficial cells on the front of the cornea to become damaged and die off," said Dr. Lee Duffner, an ophthalmologist in Hollywood, Fla. Photoconjunctivitis is a similar inflammation that affects the conjunctiva, the membrane lining the inside of the eyelids and the eye socket. Both conditions can be very painful, but people tend to recover quickly from them with no long-term damage to their vision.

Long-term UV exposure can do cumulative eye damage over time, causing more insidious and dangerous threats to a person's vision, including:

• Pterygium. An abnormal growth of the conjunctiva caused by sun damage that can become so large it grows over and obstructs the cornea, partially blocking vision. Surgery may be required to restore vision. "The bad ones have a tendency to come back, even after they're removed surgically," Duffner said. "They're a real nuisance."
• Cataracts. These involve clouding of the eye's lens. Ultraviolet rays are believed to play a part in the process.
• Macular degeneration. UV rays that penetrate deep into the eyeball are believed to do damage to the retina, the sheet of nerves along the back wall of the eye that perceive light. The macula, at the center of the retina, is responsible for perception of fine details and a person's central field of vision. "Chesapeake Bay sailors who wear sunglasses and a hat have a much lower incidence of cataracts and macular degeneration than those who don't," Martinez said, citing research.
• Cancer. People can develop skin cancer of the eyes as a result of UV damage, according to the WHO. The eye tends to develop melanoma, while the eyelids usually are inflicted with basal cell carcinoma. In both cases, surgery may be necessary.

Of course, such damage doesn't occur just in the summer, or even just when you're standing in sunshine. Bright reflected sunlight from sidewalks, aluminum, snow and other surfaces can cause UV damage just as easily as direct sunlight. In fact, one of the more well-known forms of photokeratitis is snow blindness, which occurs when skiers and climbers are exposed to high levels of UV radiation from light reflected off snow.

So how to protect yourself? Sunglasses. It's that simple, the experts say. A wide-brimmed hat wouldn't hurt, but sunglasses are key.

The sunglasses should be rated to absorb 99 to 100 percent of both UV-A and UV-B radiation. Read the labels. And keep in mind that how much you pay may not guarantee protection.

"It's not really price-related," Duffner said. "I've seen very expensive sunglasses that are not good ultraviolet absorbers, and I've seen cheap sunglasses that were great ultraviolet absorbers."

Also, toss fashion sense out the window, the eye experts say. Small, stylish sunglasses will allow UV radiation to reach the eyes. "If possible, buy wrap-around sunglasses," Duffner said. "With a standard pair of glasses, a fair amount of sunlight still strikes the eye from the side."

The worst forms of UV-related eye disease come from accumulated damage, making it important to start protecting kids' eyes so they will have a better chance of maintaining their vision in their old age.

The bulk of exposure occurs in the first 18 years of life," Martinez said. "The more sun damage you have, the more sensitive you are to later exposure. The trick is to try to get kids to wear sunglasses. It's difficult, but you must try."

More information

Prevent Blindness American has more on protecting eyes from the sun.

For more on UV damage to the eyes, read one woman's story.