Sunglasses are an easy solution that makes life more comfortable when outdoors, while also providing critical protection from the sun’s damaging ultraviolet (UV) rays.
Long-term exposure to UV rays can damage the eye’s surface as well as its internal structures, sometimes contributing to cataracts (clouding of the lens) and macular degeneration (breakdown of the macula).
Ophthalmologists and optometrists now recommend wearing sunglasses and a brimmed hat whenever you’re in the sun long enough to get a suntan or a sunburn, especially if you live at a high elevation or near the equator.
The good news is that sunglasses don’t have to be expensive to protect your eyes and they can often be found at the local drugstore. Unfortunately, a high price is not always a guarantee of high quality and protection. Part of the difficulty is that standards and labeling regarding UV protection are voluntary, not mandatory—and can be confusing.
Here are some things to keep in mind when shopping for sunglasses:
Look for UV protection
Don’t be deceived by color or cost. The ability to block UV light is not dependent on the darkness of the lens or the price tag. While both plastic and glass lenses absorb some UV light, UV absorption is improved by adding certain chemicals to the lens material during manufacturing or by applying special lens coatings. Always choose sunglasses that are labeled as blocking 99-100% of UV rays. Some manufacturers’ labels say "UV absorption up to 400nm." This is the same thing as 100% UV absorption.
Wraparounds offer added protection. Sunglasses that wrap around the temples prevent the sun’s rays from entering from the sides. Some studies have shown that enough UV rays enter around standard sunglass frames to reduce the protective benefits of the lenses.
Ensure they block enough light
Sunglasses should screen out 75-90% of visible light. To determine if a pair is dark enough, try the glasses on in front of a mirror. If you can see your eyes easily through the lenses, they probably are too light.
Check lenses for quality
Look for a uniform tint, not darker in one area than in another. To check for imperfections in the lenses, hold the glasses at arm’s length and then look through them at a straight line in the distance, such as the edge of door. Slowly move the lens across the line. If the straight edge distorts, sways, curves or moves, the lens is flawed.
Determine which special features you need or want. Like cars, sunglasses often have a variety of "extras" from which to choose:
Polarized. Polarized lenses cut reflected glare—when sunlight bounces off smooth surfaces like pavement or water. These can be especially helpful when driving, boating or out in the snow. Polarization is unrelated to UV protection, so you still need to ensure UV absorption of the lenses.
Mirror coatings. These thin layers of various metallic coatings can reduce the amount of visible light entering the eyes. They are popular in high-glare environments and when combined with the wraparound feature, they can even provide added protection to the skin surrounding the eye area. UV protection, however, is not guaranteed.
Gradient. These lenses are permanently shaded from top to bottom or from top and bottom toward the middle. Single gradient lenses (dark on top and lighter on the bottom) can cut glare from the sky but allow you to see clearly below—good for driving, for example, but not as helpful in the snow or at the beach. Double-gradient lenses (dark on top and bottom and lighter in the middle) may be better for sports where light reflects up off the water or snow, such as sailing or skiing.
Photochromic. This is a type of lens that automatically darkens in bright light and becomes lighter in low light. Although photochromic lenses may be good UV-absorbent sunglasses (again, the label must specify this), it can take a few minutes for them to adjust to different light conditions.
Impact resistant. While all sunglasses must meet minimum FDA standards regarding impact resistance, no lens is truly shatterproof. Plastic lenses are less likely to shatter upon impact than glass lenses. And, polycarbonate plastic, used in many sports sunglasses, is even more impact resistant than regular plastic, but scratches easily. If you buy polycarbonate lenses, look for ones with scratch-resistant coatings.
Remember, even the best sunglasses cannot protect your eyes from certain intense light sources. Arc welding, tanning lights, snowfields or gazing directly at the sun (even during a solar eclipse) all require special protection to prevent damage.
References: Glaucoma Research Foundation>