Pop quiz: When should you wear sunglasses?  

• At the beach 
• When walking your dog 
• Driving your car 
• When it’s cloudy 
• During winter 

If you answered “all of the above,” ding, ding, ding! Right answer! And there are countless other situations that belong on this list, because the best time to sport shades is any time it’s light outside. 

Sunglasses are crucial in blocking the ultraviolet light that increases the risk of numerous eye diseases, including cataracts and macular degeneration, according to the American Academy of Ophthalmology. These conditions can impair your vision and interfere with your ability to do everyday tasks, such as reading and driving safely.  

You don’t have to spend a ton on sunglasses, but a super cheap pair might not offer enough protection for your eyes. We asked Robert Simon, O.D., an optometrist with Nashville Regional Eye Care, located inside America’s Best Contacts & Eyeglasses in Hermitage, Tennessee, how to wade through the different types of sunglasses. Here’s what you need to know to find a protective pair that will look good too:   

What does an optometrist look for in a good pair of sunglasses? 

Everyone wants to see like a hawk and look like a movie star, says Dr. Simon, diplomate of the American Board of Optometry. But there are a few things you should consider when buying a pair of sunglasses. 

“Good sunglasses should protect your eyes against the sun. They should adequately cover your field of vision, with no sunlight peeking through. They should also be distortion-free,” he says. “And you can get these things at all price points.”  

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When trying on pairs in the store, how do you know if they offer enough protection? 

Most important, you want a pair that boasts 100% UV protection to ensure that the lenses are effectively blocking both types of rays that can reach your eyes and skin: UVA and UVB rays. UVA rays are the intense, long-wave rays that can pass through your eye’s cornea and reach the lens and retina. UVB rays are the short-wave rays that can burn your skin.  

You can’t assume that just any pair will have the proper protection. In fact, according to an AAO survey, less than half of purchasers don’t check the UV rating before buying. Be smarter than those consumers: Buy sunglasses only with lenses labeled “100% protection against both UVA and UVB” or “UVA 400 protection.”    

If you’re concerned that the shades you’ve had for years might not offer enough protection, take them to your optometrist, who can quickly test them for you. 

“I like sunglasses with lenses that are dark enough that if you were to go into a restaurant, you’d have to take them off because it would be too dark to see,” says Dr. Simon.  

Are cheap sunglasses okay? 

A bargain pair of shades can still be plenty protective, but don’t make the mistake of judging them by how dark their lenses look. The color and darkness of the lenses have nothing to do with the lens quality and the sunglasses’ ability to block UV rays — you need that “100% protection” or “UVA 400” label.  

In fact, super dark lenses without sufficient UV protection can be a hazard: Because they’re so dark, your pupil responds by dilating and allowing more damaging UV light than normal to enter the eye.  

When you’re searching for a deal, also be on the lookout for distortion, which is a common problem with poorly made glasses, says Dr. Simon. If you put them on and notice that straight lines (such as the tile edges on the floor) appear a bit wavy, skip them. Distortion causes your eyes to struggle to see clearly, which leads to eyestrain and fatigue. A well-made pair of glasses will offer a sharp, clear picture. 

 “While a nice pair of sunglasses doesn’t have to break the bank, your eyes can suffer if you purchase an extremely cheap pair,” he says. 

Does it matter how they look? 

The color of your glasses’ lenses is largely a matter of personal preference, but it can affect how you see objects. “If you’re in search of colored lenses, I’d recommend gray,” says Dr. Simon. “Gray allows you to see all colors equally across the spectrum without altering the colors you see outside.”   

When it comes to shape, bigger is better. Larger sunglasses simply protect more of your face. Wraparounds block rays from the sides too, which offers additional security for your eyes as well as the skin around them. It’s also important that your new shades properly fit on your face. If they’re too big, they leave openings at the sides or may slide down your face, leaving gaps in protection.  

Should I spring for extra bells and whistles, such as photochromic or polarized lenses? 

Photochromic lenses — they transition from dark to clear depending on the surrounding light — are a convenient option. “If you don’t want to carry around two pairs of glasses, their convenience is worth it,” says Dr. Simon. “Wearing them may help you remember to wear sunglasses more regularly, which is a good thing. It’s helpful to talk to your optometrist or optician about what’s best for your lifestyle.”  

As for polarized lenses, they’re especially useful if you play water or snow sports or you fish, he says. Light waves, especially those bouncing off water or snow (or anything shiny), hit your eyes from multiple directions. Polarized glasses have a light-filtering chemical applied to the lens that lets only a portion of those rays pass through, helping you see details more clearly.    

If you want your sunglasses to include your vision prescription, you’ll need to see your optometrist, of course. But even if you simply want to be sure your regular shades have the best protection you can get, your optometrist is a great source for advice.