Sunglasses rank somewhere in our fashion sensibility among handbags and shoes. We usually choose a pair as much because of the way they look as we do for their functionality. Wait, who am I kidding? Most people choose them mainly for how snazzy they look. Just check out the sunglasses wall at Target. It’s a veritable carnival for colors and shapes.

Obviously sunglasses reduce squinting, helping you thumb your nose at premature crow’s feet. But they are actually a prophylactic medical device, too. A quality pair will protect your eyes from nasty stuff like vision-blocking tissue growth, cornea sunburns, and eye cancers. But as a cosmetic dermatology pro, I want to tell you how often skin cancers crop up around the eyes. Because sunscreens aren’t supposed to be slathered around your peepers, we actually see a lot of skin cancers there. Those darn carousels of $5 sunglasses in drugstores and gas stations shoulder some blame.

I won’t knock all cheap sunglasses. The vast majority of them now minimize sun damage, but some still don’t. Sunglasses need to offer substantial UVA and UVB ray protection—at least 95 percent and preferably more like 99 percent. (In addition to guarding against wrinkles and skin cancers, this protection also addresses the problem of more light trying to enter the eyes due to darkened lenses dilating the pupils.)

By the way, sunglasses should also be more than just two round lenses set in a frame. The best ones wrap around the eyes so sunlight won’t sneak in from the sides and have a heyday there. Face it: I can help you undo wrinkles from years without wraparound sunglasses, but it is obviously best to avoid getting them in the first place!