Kai Pfaffenbach/Reuters
It's almost summer, and time to start stocking up on the universal sunny-day accessory: sunglasses.
It might be tempting to grab a pair from your nearest dollar store and hit the beach. But if you do that, you probably won't be doing yourself - or your vision - any favors.
Ultra-violet (UV) light, the same rays that cause sunburns and skin cancer, is invisible to the human eye. Enough exposure can have damaging effects on your eyes, potentially causing cataracts, macular degeneration, and other conditions that affect vision.
And while cheap sunglasses may feel like they're helping, they could actually be making the problem worse. When your surroundings get darker - like walking into a dimly lit room, or slapping on those dollar shades - your pupils (the black dots in the middle of your eye) open wider to let in more light.
But if those sunglasses don't block UV radiation, your eyeballs are actually more exposed to the rays than they would be otherwise.
So what's a sun-worshiper to do?
Jordan Strauss/AP
Listen closely, Bieber.
First of all, it's worth noting that you don't have to spend hundreds of dollars for adequate protection. You can find good, UV-blocking shades for $20 or so - just make sure they're labeled with a sticker that says they block 95% to 100% of UV rays; or claims "UV absorption up to 400nm," which means 100% blockage.
The non-prescription sunglass industry isn't well regulated, so claims like "blocks most UV rays" don't mean a thing. However, the US Food and Drug Administration does demand that specific claims, like 99% or 100% UV absorption, must be true. Hard numbers are the only way to know you're getting the protection you need.
The American Academy of Opthamology (AAO) has some other helpful tips to help you pick the right pair: Larger sunglasses mean more coverage, which is better (all the more reason to invest in a pair of celebrity-sized specs).
The AAO also recommends polarized lenses, which don't block UV rays but do cut down on glare for better visibility generally.
It's worth noting that lens color and darkness don't matter. So if you've got a pair of rose-colored glasses, go ahead and wear them - as long as they promise to block 100% of UV rays.