by Deanna Mayo
It is finally beginning to feel like spring is here and Michigan we will once again start to see the sun. As much pleasure as enjoying the warm sun brings, we must also remember to protect our eyes from its potentially harmful ultraviolet (UV) rays.
UV radiation reaches us in two forms, UV-A, and UV-B. UV-B represents the short wavelength radiation that causes sunburn and skin cancer. UV-B has a higher energy than UV-A but most of it is absorbed by the front layers of the eye. UV-A radiation has a lower energy, but is able to penetrate much deeper into the eye. Scientific evidence shows that exposure to both UV-A and UV-B can have damaging long and short term effects on your eyes and vision.
Short term exposure to excessive UV radiation can cause a condition called photokeratitis. This extremely painful condition can result in temporary loss of vision. Fortunately, like a sunburn, it is usually temporary and in most cases does not cause permanent damage to the eye.
Long term exposure to UV radiation can have more serious consequences. Laboratory studies have shown that UV radiation is a contributing cause to cataracts, a clouding of the lens of the eye. Scientists have also speculated that that chronic UV exposure may also contribute to a disease called age-related macular degeneration by contributing to the aging processes in the retina.
The risk of ocular damage from UV exposure is highest when the radiation from the sun is most intense. Mid-day hours, between 10am and 3pm, and summer months are when the sun is most direct and therefore adds to exposure risks. In addition, the risk is higher when on the beach, on the water, or on the slopes, due to reflections from the sand, water, and snow. Being closer to the equator and higher in elevation also increases risk.
Although everyone is at risk, some individuals should take extra precautions. People who have had cataract surgery are at increased risk of retinal injury from sun exposure because the human lens absorbs UV radiation. Most lenses inserted during surgery will provide some UV protection but additional protection is still recommended. Retinal dystrophies or other chronic retinal diseases may put individuals at greater risk also. Many prescription or over-the-counter medications can increase your sensitivity to UV radiation. Check with your eye care doctor, primary care physician, or pharmacist to find out.
Children frequently spend more time outdoors than adults, and it is important that their eyes are properly protected from the sun's radiation. The combination of a hat and sunglasses will offer the best solution. Children's sunglasses should have lenses made of plastic (preferably polycarbonate or Trivex), not glass, for added impact protection.
To provide protection for your eyes, you need to find sunglasses that block 99-100% of UV-A and UV-B in addition to screening out 75-90% of visible light. The best lens color choices are gray, green, or brown. Blue blockers are sunglasses with amber lenses that block blue light. Because blue light scatters in the eye, these lenses may increase your contrast in certain situations, however research has not established their effectiveness.
Sunglasses have other options available to fit your needs. Polarized lenses block reflected light from the surface of water and are good for boating or driving. Photochromic lenses adjust their darkness when the intensity of UV light changes. Wrap around frames provide added protection from the sun. Contact lenses are now available with a UV-blocking feature, however, they absorb less than the recommended 99-100% of UV-A and UV-B radiation. These should still be worn with sunglasses outside to provide additional protection.
When buying sunglasses, don't be fooled by misleading labels. The American Optometric Association offers a Seal of Acceptance to sunglasses that block 99-100% of UV radiation. Look for this seal or a label stating "100% UV protection" not just "UV protection". Price is generally not a reliable indicator of the lens quality or UV protection so should not be used in determining UV safety.
For more information, talk to your eye care practitioner or check out the All About Vision website http://www.allaboutvision.com/sunglasses/. It's time to start enjoying the summer sun, but don't do it without adequate UV protection for your eyes!