The sun is a welcome sight for most people. It makes us feel good. But too much is dangerous. It can cause painful blistering sunburns and long term problems like skin cancer and cataracts.

Ultraviolet (UV) radiation is invisible. It is the high-energy rays from the sun beyond the violet/blue end of the visible spectrum. Ultraviolet radiation is divided into two major bands, UV-A and UV-B. UV-A is longer wavelength radiation, close to blue in the visible light spectrum. It tans the skin and has been implicated in skin aging. UV-B is more active, shorter wavelength radiation that causes blistering sunburn and is associated with skin cancer. Most UV radiation is absorbed by the anterior structures of the eye, although some of it does reach the light-sensitive retina. UV absorption by the eye may be a causative factor in a number of serious eye diseases. Protection is simple, safe, and inexpensive.

Sunlight-related eye diseases

Cataracts are a cloudiness of the lens inside the eye, which occurs over a period of many years. UV radiation can be a factor in cataract development.

Macular degeneration is a serious age-related eye disease and a major cause of legal blindness among Americans over age 50. Exposure to UV and intense violet/blue visible radiation may contribute to aging processes in the retina.

Pterygia are growths on the white of the eye that extend onto the cornea. It is seen most commonly in people who work outdoors in the sun and wind and is related to the amount of UV exposure. It can be removed surgically, but often recurs. They can cause cosmetic concerns and visual loss if untreated.

Skin Cancer can be caused by excessive UV exposure.

What situations increase UV exposure?

Individuals whose work or recreation involves lengthy exposure to sunlight are at greatest risk.

UV is reflected off surfaces just like visible light, so skiing, boating and beach-going will increase UV exposure. UV intensity is greatest during the midday hours and during summer months. Ultraviolet radiation levels increase nearer the equator, so residents in the southern U.S. are at greater risk. UV levels are also greater at high altitudes.

Are children at risk?

Yes. They typically spend more time outdoors in the sunlight than adults do. Solar radiation damage to the eye may be cumulative and may increase the risk of developing an ocular disorder later in life. Protect the eyes of children against UV radiation by wearing a brimmed hat or cap and sunglasses. Sunglasses for children should have lenses made of plastic rather than glass for added impact protection.

Are sunglasses enough?

A brimmed hat blocks roughly 50% of the UV radiation and reduces UV radiation that may enter above or around the sunglasses. Ultraviolet-absorbing eyewear provides the greatest measure of UV protection, particularly if it has a wraparound design to limit the entry of peripheral rays.

UV absorption can be incorporated into nearly all optical materials currently in use and does not interfere with vision. Lenses do not have to be dark to provide UV protection. Polarized lenses and lenses that change tint with light level are additional sunglass features that are useful, but do not, by themselves, provide UV protection.

For outdoor use in the bright sun, sunglasses that absorb 99-100% of the full UV spectrum to 400 nm are recommended.

Currently there is no uniform labeling of sunglasses that provides adequate information to the consumer. Labels should be examined carefully to insure that the lenses purchased absorb at least 99-100% of both UV-B and UV-A. Consumers are advised to be wary of claims that sunglasses "block harmful UV" without saying how much.

Opticians at Harvard Vanguard Medical Associates Optical Shops can test your lenses for the amount of UV protection.