Sunglasses:
What to Look for in a Pair of Sunglasses
by Orlin Sorensen
Summer's almost here! However you choose to have fun in the sun, buying the right pair of sunglasses is the bright thing to do.
Sunglasses reduce the total amount of light reaching the eye and, in particular, protect the eye from the damaging ultraviolet (UV) part of the spectrum. Ultraviolet rays are located just past the violet portion of the visible light spectrum - sunlight is their main source. Having a wavelength shorter than wavelengths of visible light and longer than those of X rays, UV rays are divided into three ranges: A, B and C. Prolonged exposure to UVA and UVB can cause significant eye damage to the cornea, retina, and lens, from temporary discomfort to long-term vision problems such as cataracts and cancer. UVC is not considered a threat because much of it is filtered by the earth's protective ozone layer (although pollutants are degrading the ozone, thus increasing UV exposure). Recent studies indicate that greater amounts of the sun's UV radiation are reaching the earth's surface.
Good sunglasses can eliminate UV rays completely. They also provide protection from glare - the reflected light from snow, sand, or water, for instance - which can also harm the eye. With seemingly endless styles to choose from, however, how do you pick the right ones?
1) Expensive does not always mean protective.
What really counts is the degree to which the lenses filter out UV rays. Make sure your sunglasses have a statement on the label telling you how much UV protection they offer. The American Optometric Association offers a Seal of Acceptance for sunglasses that block 99 percent to 100 percent of UV radiation. Look for this seal to be sure you are getting the maximum protection.
The website "How Stuff Works" describes an easy way to tell if the lenses in a pair of sunglasses are of good quality. Find a surface with repeating lines, like a tiled floor. Hold the sunglasses a short distance away from your face and cover one eye. Look through one of the lenses at the lines while moving the sunglasses slowly from left to right and then up and down. The lines should stay straight as you look at them. If they wiggle or waver in any way, then the lenses are not optical quality and will distort your vision.
2) Darker is not always better.
Although it would seem that the darker the sunglasses, the more light they block, in fact dark sunglasses may still allow UV rays to enter the eye. They can even be more harmful than wearing no glasses at all, because they cause the pupil of the eye to dilate, which allows more UV rays to enter. It's a special coating on the lens that makes them safe, not their darkness.
That said, what you plan to use the sunglasses for determines the darkness of the tint. For outdoor sports, such as mountain climbing and skiing, you want a tint that blocks most light. For most purposes, like going to the beach or driving, look for a tint that absorbs or blocks 70 percent to 90 percent of light. Tints that offer less than 60 percent blockage may be fashionable, but offer only mild protection. While purple and blue tints may be fun, optimal sunglass lens colors are gray - which does not modify colors - green, and brown.
3) Choose the special feature that's right for you.
Polarizing lenses, which reflect glare from snow, water, and roads, are good for skiers, boaters, and cyclists. Photochromic lenses darken or lighten with the amount of light present and may be useful if weather conditions are erratic. Mirror coatings are best for intense glare (snow or water). Wraparound and close-fitting frames block more glare, wind, and debris around the sides of the eyes. New contact lenses are available with built-in UV protection, and the field is developing quickly. And don't forget the little ones: Kids need sunglasses too!
4) Keep 'em clean.
Scratched lenses will scatter the sun's light and could cause glare around the area of the scratch. Look after sunglasses by keeping them in a case and cleaning them with a mild detergent and water or a special lens cleaner. When drying lenses, do not use a paper towel, as this will scratch the lens. The solution is to use a good cloth, preferably one made of microfibre.
These tips can help you choose a pair of high-quality sunglasses that will protect your eyes for years to come. Your optometrist can also advise you before making a sunglass purchase. If your sunglasses are safe as well as stylish, you've got it made in the shade this summer!
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