Why Sunglasses Are So Important
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).
Sunglasses are eyewear designed to help protect the eyes from excessive sunlight. Eyes are extremely light sensitive and can be easily damaged by overexposure to radiation in the visible and nonvisible spectra. Bright sunlight can be merely a distracting annoyance, but extended exposure can cause soreness, headaches, or even permanent damage to the lens, retina, and cornea. Short term effects of sun overexposure include a temporary reduction in vision, known as snow blindness or welders’ flash. Long-term effects include cataracts and loss of night vision. In both cases, the damage is caused by Chronic ultraviolet (UV) light, which literally burns the surface of the cornea and cause 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.
Sunglasses were originally invented to reduce distracting glare and allow more comfortable viewing in bright light. Early sunglasses were simply tinted glass or plastic lenses that were primarily meant to reduce brightness. Darker lenses were considered to be better because they screened out more light. As our understanding of the damaging nature of sunlight evolved, the need for better eye protection was recognized, and technology was developed to help sunglasses better screen out the harmful rays of the sun, especially UV rays. From inexpensive models with plastic lens and frames to costly designer brands with ground glass lenses and custom-made frames, sunglasses are available in a staggering array of styles and prices. Unfortunately there is no way to tell from the color or darkness of the lens how well it will screen out UV light. Similarly, there is little relationship between price of glasses and their ability to block UV light.
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 extra features. Just make sure they are UV treated, since these features are not related to UV protection.
Polarized lenses cut down on reflected glare, which is good if you are driving, boating, fishing or skiing, for example—but they make it harder to see cellphone, ATM and dashboard displays.
Mirrored lenses can be helpful in very bright conditions, though they scratch easily. The tint of the mirror coating doesn’t affect color perception.
Photochromic lenses automatically darken and lighten depending on the ambient light. It takes about 30 seconds for them to darken in bright light, but about five minutes to fully lighten when you go inside.
Gradient lenses are shaded darker at the top and lighter at the bottom, which cuts light from the sky but allows you to see the car dashboard and horizon well. They also let you see your step as you enter an area with less light. Double-gradient lenses are dark at the top and bottom and are good for skiing, boating and water sports.
Ultra-impact-resistant lenses are good for certain sports and occupations. The Food and Drug Administration (FDA) requires all eyeglasses to be impact-resistant, but polycarbonate lenses are the most shatterproof. They scratch easily, however, so look for ones with scratch-resistant coatings.
- University of California Berkeley: Berkeley wellness