Sunglasses and UV Light: Q&A
Q: I've heard that cheap sunglasses can be more damaging to your eyes than wearing no sunglasses at all. Apparently, when one wears sunglasses the pupil widens; if the sunglasses have poor UV protection, then the eyes are damaged more by the sun's rays. Is this correct, or are any sunglasses better than none? G.H., Malaysia
A: I have heard this as well, but I've never seen any confirming studies. It does sort of make sense, though. But remember, even clear lenses can have 100 percent UV protection.
Having said that, I do highly recommend quality lenses for best comfort and vision both in regular glasses and sunglasses. Why take chances with your eyes? Dr. Dubow
[If you're wondering how high the UV light levels are where you live, here's a UV index map for the United States, updated twice a day by AccuWeather.]
Q: How can I find inexpensive sunglasses that are guaranteed to block 100 percent UV? Many are made in China and say 100 percent UV protection. But how do I really know? An answer to this could help many people who cannot afford higher prices. M.D., North Carolina
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A: The amount of UV protection that sunglasses provide cannot be determined by the color of the lenses, the country of origin or the price of the eyewear. The determining factor is the lens material and any additional UV-blocking coatings that may be applied. Uncoated plastic sunglass lenses block about 88 percent UV; polycarbonate lenses block 100 percent UV.
Many cheap sunglasses use a material called triacetate. This material absorbs only about 40 percent of the UV rays. Lenses may also be made of other acrylic materials, which will vary in how much UV protection they provide.
All sunglasses with polarized sunglasses block 100 percent UV, regardless of the lens material or price of the eyewear (though polarized sunglasses tend to be more expensive than sunglasses without this extra glare-blocking feature).
To know that your sunglasses provide 100 percent UV protection, purchase them from reputable companies, specialty sunglass stores or from an optical professional. Mark Mattison-Shupnick, master optician
Q: What is the best color for prescription sunglass lenses? I was given red, and I do not think they are very protective. Plus, they change the color of things, and there are red spots in them. J.N., Pennsylvania
A: Sunglass lens colors are really a personal preference. As you noticed, some change your perceptions of color, brightness and contrast, and some don't.
The most important feature to look for in a sunglass lens is how much UV radiation it absorbs you want 100 percent for maximum protection.
It is also important to get lenses that are ground rather than punched, to minimize distortion.
A color we call neutral density gray will darken the world but not change your color perceptions. The lens tint I prefer in my sunglasses is called G-15, which is a combination of gray and green. It is the original tint that Bausch + Lomb used in their Ray-Ban sunglasses for pilots. Dr. Dubow
[My personal favorite is brown polarized lenses. The polarization cuts glare so I can see even hazy-day landscapes in sharp detail. And the brown tint gives everything a warm glow that makes the world look like a beautiful painting. L.S.]
Q: Are there any doctor recommendations for polarized sun lenses? L.K., Ohio
A: Polarized lenses are great for those who spend time on water, drive a lot, etc. The polarization actually cuts out the light coming from the horizontal meridian while allowing in the light coming in from the vertical meridian. In other words, it blocks the light that reflects in from water or the highway, reducing glare.
Most professional optical dispensaries have a demonstration display of how polarization works check it out. Dr. Dubow
Q: Can't sunglasses be dangerous for the eyes because they dilate the pupil and cause extra UV exposure onto the lens? R.G., Illinois
A: Well, yes. But NOT good quality ones. Properly manufactured sunglasses absorb 100 percent of the ultraviolet (UV) rays that can damage your eyes. If you have doubts about your sunglasses, many eye care practitioners and optical shops have little machines that can measure the amount of UV a lens can absorb. It takes just a few seconds to read the UV meter to ensure you are properly protected. Dr. Dubow
Q: After being in the sun all day I am unable to see well for weeks. I then have a problem of having enough light to see well. H.K., Illinois
A: Without examining your eyes, I cannot tell you why you are having these problems. You may be experiencing some sort of temporary damage to your eyes from UV radiation a condition commonly called snow blindness.
The technical term for snow blindness is photokeratitis. Essentially it is a sunburned eye, and it can occur whether or not you are near snow. The reason it's called "snow blindness" is because snow is highly reflective and the sun's UV rays are stronger at higher altitudes, so the risk of photokeratitis is especially high if you are skiing or snowboarding without sunglasses on a sunny day. But you can get sunburned eyes any time of year at any elevation if you spend enough time outdoors without UV-blocking sunglasses.
Your symptoms are unusual, though, because vision problems from snow blindness typically resolve within a few days. I strongly suggest you see an eye doctor for a thorough evaluation. Dr. Dubow
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Q: I'm out in the sun every day gardening, etc. I always wear large hats. Do I still have to wear sunglasses? B.P., Florida
It is important to get sunglasses that block 100 percent of the harmful UV and have good optical quality. I recommend going to an optician or eye doctor's optical shop because ineffective dark glasses can mislead you into exposing your eyes to excessive doses of radiation. Good sunglasses do not have to be expensive.
The newest trend is to get sunglass clips that fit your frames. These can be very effective in protecting your eyes if they are of good quality. Dr. Dubow
Q: Can you tell me what the difference is between anti-reflective lenses and polarized lenses? No one seems to want to, or perhaps they're just not able to answer this question for me. D.L., New York
A: Anti-reflective lenses simply cut out most of the reflections caused by light bouncing between the two lens surfaces and interfering with good, comfortable vision.
Polarized lenses cut out light from one whole meridian, typically the horizontal one. This minimizes the glare from light that bounces off water, the hood of your car or a shiny road surface. Polarization is useful for fishermen or people that do a lot of driving, though many outdoors people prefer polarized sun lenses.
Polarization is usually applied only to sun lenses, whereas anti-reflective coatings can be used on both indoor and outdoor glasses with success. Dr. Dubow
[Page updated December 2015]