Ultraviolet Rays and Your Eyes
Fashion aside, sunglasses serve a true function — protecting eyes from the harmful rays produced by the sun. You're probably well aware of the need to protect your skin from the sun, but it's equally important to protect your eyes.
Ultraviolet Light's Dangers - Ultraviolet (UV) radiation consists of invisible rays from the sun. The three bands of UV light are: UVA, UVB and UVC. UVC rays are of little concern as they are absorbed by the upper atmosphere and do not reach the earth's surface.
UVB rays are the ones that burn the skin and can damage the eyes. Combined with cold wind and snow, UVB has the potential to cause snow blindness (photokeratitis), a temporary (lasting 12 to 48 hours) but painful problem in the cornea of the eye.
Although not all experts and scientists agree, there is some research that suggests that daily exposure to UVB in very bright sunlight over a period of many years may cause cataracts, a gradual clouding of the lens of the eye.
UVA rays are primarily absorbed within the lens of the human eye, though there are no documented disorders of the human eye from UVA. This, however, remains a much debated and researched topic, says the Sunglass Association of America (SAA).
What to Look for When You're Buying Sunglasses
Sunglass standards for lenses place limits solely on UVB and UVA rays, but bear in mind that both the standards and labeling are voluntary, not mandatory. According to these standards, sunglasses must block at least 70% of UVB and at least 60% of UVA.
To best protect your eyes, look for sunglasses that provide at least 98% protection from both UVA and UVB rays. UVC rays are blocked automatically since they are absorbed in the atmosphere and do not reach the earth. Some of the higher-priced products with polycarbonate, glass or plastic (CR-39) lenses can claim to block 100% of the UV rays.
Is It True That ... ?
One question people ask frequently is whether pupil dilation from wearing sunglasses can cause problems for the eyes. The answer to this is that there is a very minimal dilation of the eyes when wearing sun protection and that the protection received from wearing sunglasses is greater even than simply standing in the shade. According to the SAA, sunglasses "reduce the UV more than if you were to stand in the shade, since the shade more or less evenly attenuates all wavelengths, visible and UV, while sunglasses preferentially attenuate shorter wavelengths (i.e., UV wavelengths)." Thus, sunglasses provide more protection.
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