Due to publicity and coverage by the news media many of us have become aware of the risks of sunburn and skin cancer from ultraviolet radiation of the sun. But did you also know that Ultraviolet radiation from the sun can harm your eyes? New research has shown that the sun's high-energy visible (HEV) radiation, which is also known as "blue light", can also harm your eyes. For pilots this is a critical issue because their eyes are exposed to higher levels of radiation due to the altitudes they fly at, and also because regardless of the time of the year most pilots fly above the clouds in the crisp, cool atmosphere where the sun's rays are strongest. Research has shown that extended exposure to the sun's UV rays has been linked to such diseases of the eye as cataracts, macular degeneration, pingueculae and pterygia, and also to photokeratitis which can cause a temporary loss of vision. To protect your eyes from harmful solar radiation a high-quality pair of sunglasses should always be worn to provide the best protection by blocking UV rays and limiting how much stray sunlight can reach your eyes from above, beside and beyond the periphery of your sunglass lenses. A lot of people call UV rays ultraviolet light; however, this is incorrect as it is not possible to see UV rays. In fact, there are three categories of these invisible high-energy ultraviolet rays:
- UVC rays -These are the highest-energy UV rays and potentially could be the most harmful to your eyes and skin. Fortunately, the atmosphere's ozone layer blocks virtually all UVC rays. But this also means depletion of the ozone layer potentially could allow high-energy UVC rays to reach the earth's surface and cause serious UV-related health problems. UVC rays have wavelengths of 100–280 nanometer (nm);
- UVB rays - These have slightly longer wavelengths (280–315 nm) and lower energy than UVC rays. These rays are filtered partially by the ozone layer, but some still reach the earth's surface. In low doses, UVB radiation stimulates the production of melanin (a skin pigment), causing the skin to darken, creating a suntan. But in higher doses, UVB rays cause sunburn that increases the risk of skin cancer. UVB rays also cause skin discolorations, wrinkles and other signs of premature aging of the skin;
- UVA rays - These are closer to visible light rays and have lower energy than UVB and UVC rays. But UVA rays can pass through the cornea and reach the lens and retina inside the eye. Overexposure to UVA radiation has been linked to the development of certain types of cataracts, and research suggests UVA rays may play a role in development of macular degeneration.
- Not all sunglasses block 100% of ultraviolet rays;
- Wear your sunglasses even when you are in the shade because while shade reduces your UV and HEV exposure somewhat, your eyes will still be exposed to UV and HEV rays reflected from glass, buildings and other shiny objects;
- Sunglasses are even more important in winter because snow can reflect more than 80% of ultraviolet rays, nearly doubling your exposure to solar ultraviolet radiation;
- Even if your contact lenses are designed to block ultraviolet rays, you will still need sunglasses because ultraviolet blocking contact lenses shield only the part of your eye under the lens;
- Even if you have dark skin and eyes you still need to wear sunglasses. While darker skin may reduce your risk of cancer, your risk of eye damage from ultraviolet and high-energy visible light remains the same as that for someone with fair skin.