Ultraviolet Rays

What eye damage can occur from ultraviolet rays?
How can you protect yourself from ultraviolet radiation?

Ultraviolet rays are invisible light waves from the sun that carry more energy than visible light. It is this invisible UV radiation that causes damage to a person's eyes and skin. UV rays have no useful purpose for your vision.

Ultraviolet radiation is divided into three components: UV-A, UV-B, and UV-C. Because most UV-C radiation is absorbed by the earth's atmosphere, it's the UV-A and UV-B rays that are of concern when protecting the eyes and skin. UV-B rays are partially absorbed by the earth's ozone layer, but UV-A radiation is not stopped by ozone.

What eye damage can occur from ultraviolet rays?

UV-A rays cause tanning and are thought to contribute to the aging of skin, while UV-B causes sunburn. Overexposure to either UV-A or UV-B radiation can cause eye damage and skin cancer. The cornea and the lens in the front part of the eye absorb most UV-B rays, and they do not penetrate to the retina in the back of the eye. It's these rays that cause alterations to the eye's natural lens and may cause cataracts. UV-A radiation, although lower in energy, can penetrate more deeply into the eye, causing damage to the retina and leading to conditions such as macular degeneration, a leading cause of blindness.

Other eye damage from overexposure to ultraviolet rays includes pterygium, an abnormal growth on the conjunctiva (outer covering of the eye) that may gradually advance onto the cornea and require surgical removal. This particular problem occurs mostly in people who work outdoors in the sun and wind. It often recurs after surgery and if left untreated can cause vision loss. Skin cancer around the eye may also result from exposure to harmful rays. Photokeratitis is a reversible sunburn of the cornea that is painful and can result in temporary vision loss. It usually occurs if you spend a lot of time on the beach or in the snow without any eye protection.

Adults and children are susceptible to ocular damage from ultraviolet rays, and even babies and small children should be adequately protected. Midday exposure offers the greatest risk, and UV levels are greater at high altitudes and near the equator. Sun sensitivity may be greater when you take certain medications, such as tetracycline, sulfa drugs, and birth control pills. Read medication labels carefully, and consult a doctor if you have any questions.

How can you protect yourself from ultraviolet radiation?

Ultraviolet rays reach the eyes directly from the sun, as well as by reflection from the ground, particularly from water, snow, and sand. Up to 50 percent of UV radiation can be blocked by simply wearing a wide-brimmed hat, but the best eye protection from UV radiation is a good pair of sunglasses that is rated to block 99 percent to 100 percent of the full UV spectrum. The lenses should filter wavelengths up to 400 nanometers to cut out all harmful rays. Wraparound eyewear also helps minimize the amount of harmful light. Lenses that reduce the transmission of violet/blue light can provide additional retina protection. UV protection can be incorporated into all eyewear, including prescription glasses, safety and sport goggles, contact lenses, and intraocular lenses like those used in cataract surgery.

Sunglasses should not be so dark that they cut visual sharpness and detail. Light rays should be reduced to a comfortable level, eliminating glare and squinting. Although the degree of UV protection is not always related to the price of sunglasses, poorly manufactured glasses can give a false sense of security by darkening the image but not providing protection from ultraviolet radiation. They can, in fact, increase exposure by causing the pupils to open wider and letting in more of the harmful rays. Polarized and photosensitive lenses do not by themselves provide UV protection. Buy sunglasses that are labeled with the actual percentage of the UV spectrum that they block, not those that say "block most harmful rays."