Many people choose sunglasses by how they look and feel. But the most important feature to consider is how well they shield your eyes from ultraviolet rays (high-frequency invisible energy emitted by the sun), as well as blue light (high-frequency visible light).
Chronic ultraviolet (UV) exposure is implicated in a range of eye conditions, including cataracts, benign growths on the surface of the eye, skin cancer on the eyelid and around the eyes and even melanoma of the eye itself. Blue light is particularly damaging to internal eye tissues and over time may permanently damage the retina, leading to macular degeneration.
Sun damage is cumulative, so the more time you spend outdoors with your eyes unprotected, the greater your lifetime risk. The good news is that it’s not hard to find affordable sunglasses that are fashion-forward and protective.
Everyone who spends time outside should wear sunglasses. That includes children (whose eyes are especially vulnerable to UV) and people who wear contacts (even if UV-treated, they don’t cover the whole eye). Sunglasses are a necessity for people who are sun-sensitive due to medications (such as tetracycline) or other reasons, and for those who have had cataract surgery, especially if they have an older intraocular lens that provides no UV protection. Light-colored eyes are especially vulnerable to UV. Even on overcast and hazy days, your eyes can be exposed to significant UV radiation.
Here’s more reason to wear a pair: Very bright sunlight can irritate eyes—and even burn the cornea, a temporary but painful condition called photokeratitis or “snow blindness.” Sunglasses also shield eyes from wind, dust and drying, and they help reduce glare, which can be hazardous when driving, biking, or playing sports.
What to look for in sunglasses
There are no federal standards for sunglasses, and labels are inconsistent and confusing. A tag or sticker that simply says “blocks UV” or “UV-absorbent,” for instance, is meaningless because it doesn’t tell you how much UV is blocked. Better choices are sunglasses that claim to block most or all UV (“99-100% UV absorbent” or “UV 400,” for example), though there is no independent verification for this. And while the American National Standards Institute (ANSI) sets voluntary standards (Z80.3 codes) for UV protection of sunglasses, you’re not likely to see these labels, and they don’t guarantee that the glasses have actually been inspected.
One way to be certain that your sunglasses are blocking most or all UV is to have an optician test them using a photo spectrometer (often called a UV meter). It’s a good idea to have old sunglasses tested, since some of the UV coating, if one was applied, can be lost over time through scratches and abrasions. An optician can also coat sunglasses, if necessary.
More general pointers:
- Both clear glass and plastic lenses naturally filter out some UV light (polycarbonate plastic, in particular, blocks nearly all UV). But maximal UV protection comes from clear chemicals that are incorporated into the lenses during manufacture or applied as a coating.
- Darker lenses don’t mean greater UV protection. In fact, unless darker lenses are fabricated to block UV, they can be more harmful than wearing no sunglasses, because they can cause pupils to dilate, allowing more UV to enter your eyes. Darker lenses do, however, block more visible light and minimize glare. They should be dark enough so you don’t see your eyes when you look in the mirror, but light enough so you can see curbs, stoplights, and stairs.
- Colored lenses reduce visible light, but color has nothing to do with UV protection. Yellow, amber and orange lenses block the most blue light and enhance contrast, but can distort colors. Brown also blocks significant blue light. Gray and brown lenses produce the least color distortion and are good for all-around wear and driving. Green distorts minimally. Avoid blue-tinted glasses, which let in more blue light.
- The larger the frames, the better. Wrap-around glasses block light coming from the side, but may cause distortion.
- You should be able to find an adequate pair of sunglasses for $20 to $60. More expensive ones are not necessarily better, but cheap ones (less than $10) are more likely to have optical imperfections.
- To check lens quality, hold the glasses at arm’s length and look at a straight line in the distance. When you move the glasses across that line, the line should not bend.
- If you wear prescription glasses, you can buy prescription sunglasses or glasses with photochromic lenses. You can also get sunglass “clip-ons” for your regular frames—or “click-ons” that attach magnetically. At a minimum, your regular glasses should have added UV protection.
Beyond UV Protection
You can find sunglasses with all kinds of extras, from polarized lenses to gradient lenses to those that automatically darken or lighten, depending on ambient light. Just make sure they are UV treated as well.
Published August 13, 2013