Monday, December 21, 2009

UV protection for eyes

UV radiation from the sun can damage not only the skin of your eyelids but also the clear outer parts of the eye — the cornea and conjunctiva. UV exposure also contributes to the development of certain types of cataracts.

When you're choosing sunglasses, look for UV protection details on product labels. Choose sunglasses that block at least 99 percent of UVB rays and at least 95 percent of UVA rays. This level of UV protection is in accordance with guidelines established by the American National Standards Institute (ANSI). Skip sunglasses that are labeled "cosmetic" and those that don't offer details on UV protection.

Of course, UV protection isn't the only consideration when it comes to selecting sunglasses. In addition to UV protection — which, again, is a must for any type of sunglasses — here's the lowdown on other options:

  • Blue-blocking lenses. Blue-blocking lenses — which are typically yellow or orange — are thought to make distant objects easier to see, especially in low light. Blue-blocking plastic lenses may make it difficult to discriminate the hues in traffic lights, however, and not all blue-blocking lenses offer adequate UV protection.

  • Polarized lenses. Polarized lenses reduce glare. Unless they're specifically treated with UV coating, polarized lenses don't offer UV protection.

  • Photochromic lenses. Photochromic lenses reduce glare and help maintain clarity, although they may take time to adjust to different light conditions. Not all photochromic lenses offer adequate UV protection, so be sure to check the product label.

  • Polycarbonate lenses. Polycarbonate lenses offer protection from impact injuries that may be sustained during physical activities. Polycarbonate lenses also adequately shield the eyes from UV radiation.

  • Mirror-coated lenses. Mirror-coated lenses help block visible light, but they don't necessarily block UV radiation.
Standard prescription eyeglasses can also be treated with a material that provides UV protection while retaining a clear, nontinted appearance. Most rigid contact lenses also provide UV protection — but because contact lenses don't cover the entire eye, it's still important to wear sunglasses when you're outdoors.

Source : Dennis Robertson, M.D. Mayo Clinic Emeritus Opthomologist

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