Ultraviolet radiation and sunglasses
Since the development of UV Index, more and more people have paid 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 closely associated with eye diseases, such as cataracts, macular degeneration, pingueculae and pterygia, phototkeratitis and so on. In addition, HEV (high-energy visible) radiation is especially risky for people with low blood plasma levels of vitamin C and other antioxidants.
Three forms of invisible UV rays
Many people take ultraviolet radiation as UV light, but this opinion is not correct because the UV rays are not visible. There are mainly three types of invisible UV rays. With a wavelength of 100-280 nanometers, UVC rays have the highest energy and are most harmful to the 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, mainly because of the thinning ozone layer. Filtered partially by ozone layer, UVB rays are longer and less 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.
HEV and other dangerous factors
In addition, HEV (high-energy visible) radiation, with a longer wavelength and lower energy than UV rays, is related to the development of macular degeneration. In the visible spectrum, this radiation is located at the violet or blue band ranging from 380 to 530 nm. This is why it is sometimes called blue light. This high-energy light has traditionally been overlooked but it actually is a potential hazard to ocular heath in later life. Solar radiation is most widely recognized as the main source of blue light. But very few people know other artificial sources, like arc welding equipment and lasers.
Except for UV rays and HEV radiation, there are several external factors, including geographic location, altitude and medications. These factors are closely related to the degree of damage from those hazardous sources. Cloudy days may bring the same density of UV rays because they are invisible and can travel through clouds.
Get help from sunglasses
Compared to adults, children need more protection against UV rays. Kids usually spend more time outdoors than adults. The best choice of protecting the 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 do not 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.
Misconceptions of using sunglasses
There are many incorrect opinions about the protection for eyes against harmful elements. Since shade can not block UV rays and HEV radiation completely, people should wear sunglasses even in cloudy days. Customers should always keep in mind that not all sunglasses block 100 percent of UV rays. A prior evaluation from an optician is necessary. 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.
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