Sunglasses

Quiz: Test your sunglasses trivia knowledge

Woman wearing sunglasses
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Your score: 0 out of 16
1. Sunglasses that block 100 percent of UVA and UVB light rays are much more expensive than other sunglasses.

Price is not the best predictor as to how well sunglass lenses block ultraviolet light. Some expensive, designer shades don't provide good protection, while many inexpensive shades do. When you buy, make sure the label says that the lenses block 100 percent of UVA and UVB rays.

2. Children don't need to wear sunglasses, because their eyes are better able to withstand ultraviolet rays and glare than adult eyes are.

Children's eyes need sun protection just as adults' eyes do.

3. Overexposure to ultraviolet light can cause growths on the eye called pingueculae and pterygia.

Read more about pingueculae and pterygia.

4. Cataracts and age-related macular degeneration may be caused, at least in part, by too much ultraviolet light exposure.

Read more about cataracts and age-related macular degeneration.

5. If you are a mountain dweller, you will likely be exposed to higher UV levels than if you live in the lowlands.

UV exposure increases at higher altitudes because the Earth's atmosphere is thinner, and its ozone layer is therefore less effective at blocking ultraviolet radiation than at lower elevations. According to the National Weather Service, the altitude-related increase in UV exposure is approximately 4 to 5 percent for every 1,000 feet ascended. So, for example, for the same day in June, you would be exposed to roughly 27 percent more UV rays in Flagstaff, Arizona, than in Phoenix (an elevation difference of about 6,000 feet).

6. There is no reason to wear sunglasses on a cloudy day.

Haze and clouds don't prevent UV rays from reaching your eyes. UV is invisible radiation, not visible light.

7. Sunglass lenses with dark tints are more protective against ultraviolet rays than those with light tints.

Dark sunglass lenses filter more visible light than lenses with lighter tints, but that doesn’t mean they block more UV. The amount of UV protection provided by sunglasses is determined by the lens material (and sometimes a UV-absorbing lens treatment), NOT the darkness of the tint.

8. High-energy visible (HEV) light — also called blue light — is a kind of ultraviolet radiation.

HEV, or high-energy visible light, is in the visible light spectrum and is therefore not in the ultraviolet range. It is suspected as a cause of age-related macular degeneration, so certain sunglasses are designed to block HEV light.

9. Only people with light-colored eyes need sunglasses; people with dark-colored eyes are naturally protected because they have more pigment in their eyes.

Though people with light-colored eyes may be somewhat more at risk of UV-related eye damage, people of any eye color can benefit from UV protection.

10. Brown-tinted sunglass lenses are best for letting you see colors as they really are.

Gray is considered the most neutral of lens tints when it comes to color perception.

11. If you're wearing high-quality sunglasses, it's OK to gaze at the sun.

Don't stare at the sun, because it will damage your retinas, even if you're wearing sunglasses.

12. Anti-reflective coating often is applied to the back surface of sunglass lenses to reduce glare caused by light reflecting into your eyes when the sun is behind you.

Because you want less sunlight entering your eyes when wearing sunglasses, there is no reason to have anti-reflective coating applied to the front surface of sunglass lenses. Light reflecting (away from your eyes) off the front surface of the lenses reduces the amount of sunlight entering your eyes, which helps reduce glare.

But sunlight that reflects off the backside of sunglass lenses when the sun is behind you can enter your eye, causing glare and eye strain. Anti-reflective coating applied to the back surface of sunglasses eliminates this "back-scatter" problem, so AR coating is recommended for the backside of sunglass lenses only.

13. The UV Index is a 10-point scale that sunscreen lotion manufacturers devised in the 1970s to encourage people to buy their product.

The UV Index was developed by the National Weather Service and the U.S. Environmental Protection Agency in 1994, based on a similar index developed two years earlier in Canada. The UV Index provides a daily estimate of solar UV intensity to help you plan your outdoor activities and prevent overexposure to the sun's harmful rays that can cause sunburn, skin cancer and cataracts. The index estimates solar UV radiation risk on a numerical scale ranging from 1 (low risk) to 11+ (extreme risk).

14. The lowest risk level on the UV Index is indicated on UV maps with the color green.

After green come the colors yellow, orange and red, with violet representing the extreme risk level of 11+.

15. If you wear contact lenses with a UV blocker, you still need to wear sunglasses.

UV-blocking contacts can protect only the parts of the eye that are directly behind the lenses. Surrounding eye tissues will still be exposed to the sun.

16. Certain medications can increase your body's sensitivity to UV and HEV radiation.

One example is diphenhydramine, found in the antihistamine Benadryl. Others are tetracyclines, malaria medications, NSAIDs, acne medications and certain antidepressants. There are many sun-sensitizing medications, so be sure to read the label of any drug you take.

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