Q. I know I should wear sunglasses to protect my eyes, but what should I look for when I buy them?

This is a question with year-round relevance. The sun is around every day of the year. The most important feature in sunglasses is the ability to protect your eyes from invisible ultraviolet (UV) light, which also causes sunburn.

Long-term exposure to the high-energy ultraviolet radiation in sunlight is linked to eye disease. Buy sunglasses that block 99 percent or 100 percent of all UV light. Look for a label that lists protection.

If you want to be extra careful, get wrap-around sunglasses because they keep out more light. Eye doctors also recommend wearing a brimmed hat when you’re going to be in the sun for a long time.

If you don’t protect your eyes from the sun, you risk getting cataracts, macular degeneration and cancerous growths on the eye. A cataract is a clouding of the lens, the clear part of the eye that helps focus images like the lens in a camera. The macula is at the center of the retina in the back of your eye. The retina transmits light from the eye to the brain. Most eye damage caused by ultraviolet light rays is gradual and irreversible. People have different levels of sensitivity to ultraviolet radiation.

Some studies show that people with eye diseases such as macular degeneration may be at greater risk from UV rays. As a precaution, they should wear sunglasses whenever they are outdoors. This precaution is wise, too, for anyone who has had cataract surgery. If you take drugs that make your skin more light sensitive, discuss eye protection with your doctor. Medicine can make your eyes more sensitive to light.

There are other features in sunglasses that you should consider. None of these features is linked to UV protection. Remember, always check a pair of sunglasses for a UV rating.

Shade:You’ll need a dark lens if you are in bright sun frequently. However, a medium lens will suit you for most days. Sunglasses should be dark enough to reduce glare, but not dark enough to distort colors.

Color:Prevent Blindness America, a volunteer eye health and safety organization, recommends lenses that are neutral gray, amber, brown or green.

Blue Blockers:There’s a controversy over the possible harm done by blue light. There is blue light in the bright glare from snow or water. Lenses that block all blue light are usually amber-colored. This color is supposed to help you see distant objects more easily. Amber sunglasses are used by many pilots and hunters.

Polarization:Polarized lenses cut reflected glare and are especially helpful for driving.

Photochromics:A photochromic glass lens automatically darkens in bright light and becomes lighter in low light. These are convenient for people who are in and out of doors all day.

Gradients:Single-gradient lenses are dark on top and lighter on the bottom. These are great for driving. Double-gradient lenses are dark along the top and bottom and lighter in the middle. These are suitable for skiing.

Mirror-Coating:Lenses with mirror finishes reduce the amount of light that passes through to your eyes. These make an emphatic fashion statement.

Quality:A good way to check the quality of nonprescription sunglasses is to look at a rectangular pattern such as tiles. You’ll know the glasses are good ones if the lines stay straight when you move your head.

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