You may think we wear sunglasses for comfort and fashion. But here's another important reason to wear sunglasses--to protect the health of your eyes.
If you spend long hours in the sun without protection, you increase your exposure to ultraviolet (UV) rays, an invisible form of radiation from sunlight. Overexposure to UV-A and UV-B radiation causes damage to the skin and eyes. You can damage the surface of your eyes in the same way you can get sunburned--with just one exposure to extremely bright sunlight reflected off sand, snow, or water. Exposure to sunlight over years can lead to vision loss from cataracts or macular degeneration.
According to the American Academy of Ophthalmology (AAO) and the American Optometric Association (AOA), these are conditions that put the eyes of adults and children at risk:
Surfaces such as snow, sand, water, and concrete that reflect UV rays.
High altitudes or low latitudes. Exposure to UV rays is higher in the mountains or closer to the equator--in the Caribbean, for example
Time of day. UV radiation is usually at its highest from 10 a.m. to 4 p.m. As a rule-of-thumb, check your shadow; if it is shorter than you, UV radiation is at a higher intensity. If it is longer, UV radiation is at a lower intensity.
Time of year. UV radiation is higher in the spring and summer, or May to August in the northern hemisphere, and lower in the fall.
Don’t look directly at the sun. The AAO and AOA say that damage to eyes from looking directly at the sun during an eclipse is from thermal rays of the sun, not UV radiation, so sunglasses won’t protect your eyes. Don’t look directly at an eclipse.
Wear sunglasses that protect your eyes from UVA and UVB rays when you are outside; wear them even on cloudy days.
Wear a hat to provide additional protection for not only your eyes, but also your skin. Wear it even on cloudy days.
These precautions are especially important for people who have lighter skin or light-colored eyes, and for people who take medicines that increase the skin’s and eyes' sensitivity to sunlight. These medications include tetracycline, doxycycline, allopurinol, sulfa drugs, birth control pills, diuretics, phenothiazine, and psoralens.
The AAO and AOA advise against buying sunglasses that say they “block UV radiation” without saying how much is blocked. If they don’t block 99 to 100 percent, do not buy them.
Either plastic or glass lenses can absorb UV light, but the protection of either can be improved by the addition of a clear UV coating. According to the AAO and AOA, mirror coating and gradient tinting of lenses do not offer UV protection. The color and degree of darkness of lenses do not mean the lenses can block UV rays. Polarized lenses block glare, but offer no UV protection. Photochromic lenses, or lenses that change from light to dark when exposed to UV rays, may offer protection. Wraparound sunglasses keep light from shining on your eyes from the sides, offering more protection. Polycarbonate lenses offer 99 percent UV protection.
For comfort, sunglasses should be free of distortion and imperfection. Look through the glasses at arm's length and move them slowly across, up and down over a square pattern, such as floor tile. If the lines sway or wiggle, the lenses are imperfect. You also should check lenses to ensure the color is exactly the same throughout.
If you play sports, consider getting special impact-resistant lenses made from polycarbonate plastic. Get them with a scratch-resistant coating.