Related topics: •  Eye Care •  Sunscreen: How to Wear It

Sunglasses are more than a fashion accessory. Besides making you look cool, they can protect your vision, help you see the world more clearly, and even save you from crow's feet. To get the most from your shades, here are a few things to look for.

Over time, exposure to the sun's ultraviolet rays can speed the formation of cataracts, clouding your vision as you age. So look for sunglasses that block 99 or 100 percent of UV radiation. They may be labeled "UV absorption up to 400 nm," which means the same thing. (Shades labeled "cosmetic" block only about 70 percent of UV rays.) But here's the catch: The government doesn't monitor labeling claims made by sunglass manufacturers, and the chemical coating that absorbs the radiation is invisible, so you can't see whether it's there. To be sure your shades offer adequate protection, you can have them tested with a UV meter. Most opticians and some sunglass shops will do this for free.

The lenses should be dark enough to filter out 75 to 90 percent of so-called visible light, the kind that makes you squint. Besides causing eyestrain, headache, and, maybe worst of all, wrinkles, too much exposure to visible light may contribute to macular degeneration (the destruction of nerve tissue in your eyes), which is the leading cause of blindness among the elderly. Put your sunglasses on, and take a look in the mirror; if you can see your eyes, the lenses aren't dark enough to screen out visible light. Glasses called "blue-blockers" promise to shield your eyes from blue light, the band of visible light bordering UV on the light spectrum, but there's no reason to worry about this. Any lens that blocks most visible light also blocks most of the blue.

Wraparound frames offer the most protection since they block light from the sides, top, and bottom. (They also block the wind, which is why many athletes wear "wraps.") But if that style doesn't suit you, be sure to choose frames that fit close to -- but not touching -- your brow and cheekbones, and that don't slide down the bridge of your nose. (Lenses that touch your brow or cheeks may fog up or collect sweat when you're active.) Small frames may be stylish, but if the sun shines in from the top, bottom, or sides of the lenses, the glasses don't do the job. The frames should be sturdy, too. Nylon or composite frames are light and strong; wire-cored plastic can be bent for a snug fit; metal frames tend to be fashionable but are often heavy and inflexible.

Yellow or amber lenses may give the world a sunny hue, but they can make it hard to distinguish the colors of traffic signals. Stick with gray, brown, or green lenses to see the world's true colors. And glass lenses may give you a sharper view, but if you're active, polycarbonate plastic is a safer option since it's virtually shatterproof. (If you go for plastic lenses, look for a pair with a scratch-resistant coating.) To check your lenses' optical quality, put the glasses on and look at a vertical object, such as a telephone pole. Move your head from side to side; if the line seems to wiggle, choose a different pair.

These days you can buy sunglasses designed for almost any activity under the sun. Single-gradient lenses, which are permanently shaded from top to bottom, cut glare from above but allow you to see clearly below. This is good for driving since your view of the dashboard isn't obscured. Double-gradient lenses, which are dark on the top and bottom and lighter in the middle, are a good choice for snow and water sports. Polarized lenses are also great for all these activities, since they block light reflected off smooth surfaces like water and pavement. They're especially useful for flyfishing and other activities in which you need to see below the surface of the water. If you're going in and out of doors all day, you might try photochromic lenses; they darken in bright light in about 30 seconds but take about five minutes to lighten up again in dimmer conditions.

Further Resources

American Academy of Opthalmology

http://www.aao.org

References

First published May 26, 1999
Last updated February 14, 2008
Copyright © 1999 Consumer Health Interactive and OneBody, Inc.

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