As people are increasingly becoming aware of the dangers of ultraviolet rays and are learning that overexposure the sunlight may do permanent damage to their eyes, the demand has grown dramatically for lenses that can protect eyes from UV light.
Short term exposure to UV unquestionably causes a temporary inflammation for the front of the eye, resulting in redness, itching, and a gritty feeling. Of more concern, however, is the growing evidence of long term exposure to UV that can contribute to the formation of cataracts. There is also some evidence that it might contribute to some retinal disorders. Therefore, may optometrists are advocating UV-protecting glasses.
Ideally, your doctor would recommend a lens that blocks 100% of the UV rays below 390 nanometers in wavelength. Realistically speaking though, even some of the good materials might transmit 1 or 2%. This level of UV protection can be found in both dark and clear lenses, prescription and nonprescription lenses.
Shopping for Sunglasses
To judge the quality of non-prescription sunglasses, first check to see if your eyes are visible through them. If they are, then the glasses aren’t dark enough. The lenses should screen out 75-90% of the light. (This test won’t work with light-sensitive lenses like transitions or photo-gray because they are nearly clear indoors).
Next, hold the glasses at arm’s length and look through them at a straight line, like the edge of a door. Slowly move the lens across that line. If the straight edge distorts, sways, curves or moves, the lens is not optically acceptable. It’s hard enough to squint in the sun all day and yet have your body relaxed enough to play well and concentrate on a set of tennis or a round of golf. You are looking for distortion-free sunglasses.
Check to be sure that the lens tint is not darker in one area than another and that one lens is not darker than the other. Finally, check the frame, the hang-tag or the case for the level of UV protection. The closer you get to 100%, the better.
Another question you might ask your eye doctor is whether it is necessary to wear sunglasses in the winter. Even though the sun’s rays may feel less intense during the winter, they are still strong enough to worry about eye damage, including snow blindness. New snow can reflect up to 80% of UV rays, according to the World Health Organization, while normal ground surfaces and bodies of water tend to reflect less than 10%. The numbers for beach sand and sea foam are estimated at 15% and 25%.
In addition, what if you’re wearing contact lenses that have UV protection? Because such lenses can decrease the amount of UV rays the enter the cornea and affect the eye structures beneath, this is a good idea. However, you still need to wear sunglasses over contacts because UV rays will still affect the eye tissue that is not covered by the contact lenses. Your eyes will be more comfortable too, with the light and glare reduction that sunglasses provide.
If you gaze at the sun for longer than a minute, sun gazing can literally burn a hole in the retina. In the early stages, the retinal tissue swells and the retinal pigment is destroyed. Several months after the exposure, a small gray lesion will appear in the center of the macula. After several weeks, the lesion fades and is replaced by a tiny hole. Since the very center of the macula, the fovea, is responsible for sharp vision, acuity may drop to 20/200 following sun gazing. Symptoms generally develop a few hours after exposure. An aching feeling develops over the eyes and there may be a vision defect in the central field. The individual may also experience wavy vision and colour defects.
Sun gazing can inflict serious damage to sensitive retinal tissues which will result in a severe loss of vision. There is always an increase in this problem following an eclipse. Be careful!! It is important that proper glasses be used and that you never stare directly at the sun!