Ultraviolet radiation and sunglasses

Saturday, February 20th, 2010 at 2:08 pm Post in Sunglasses

Since UV Index has been developed, more and more people pay attention to the risk of sunburn and the damage of UV radiation. UV rays have been classified into five categories and their respective risk levels are low, moderate, high, very high and extreme. Long time exposure to sunshine is closed associated with eye disasters, such as cataracts, macular degeneration, pingueculae and pterygia, phototkeratitis and so on. In addition, HEV (high-energy visible) radiation may cause low blood plasma levels of vitamin C and other antioxidants.

Many people take ultraviolet radiation as UV light, but this opinion is not correct because the UV rays are not visible. The following is an introduction of three types of invisible UV rays.

With wavelengths of 100-280 nanometers, UVC rays are the highest energy and most harmful to eyes and skin. Though they are blocked significantly by atmosphere’s ozone layer, they also may travel to earth’s surface and cause health problems with the thinning ozone layer. Filtered partially by ozone layer, UVB rays are longer and lower energetic than UVC rays. They may cause skin problems and eye problems including distorted vision, corneal problems and so on. UVA rays have lower energy than UVB and UVC rays, but they can reach the lens and retina inside the eye.

In addition, HEV (high-energy visible) radiation with longer wavelength and lower energy than UV rays, is related to the development of macular degeneration. Besides UV rays and HEV radiation, there are several external factors, including geographic location, altitude and medications. Cloudy days may bring the same density of UV rays because they are invisible and can travel through clouds.

Compared to adults, children need more protection against UV rays. Kids usually spend more time outdoors than adults. The best choice of protecting eyes from sun rays is wearing good quality sunglasses with 100 percent of UV protection. Sunglasses with large lenses or close-fitting wraparound styles are better than other types. Some customers may need to buy performance or sport sunglasses during special outdoor activities. Colors of lenses don’t affect the amount of the lens’s UV protection, but they affect HEV protection. Lenses with colors such as bronze, copper and reddish-brown block blue light significantly.

There are many incorrect opinions about the protection for eyes. Customers should always keep in mind that not all sunglasses block 100 percent of UV rays. A prior evaluation from an optician is necessary. Since shade can not block UV rays and HEV radiation completely, people should wear sunglasses even in cloudy days. Sunglasses are important in winter because of the reflection of UV rays by snow. In addition, people who wear contact lenses with UV protection also need sunglasses to protect those delicate tissues and skin around eyes.