Sunlight can damage your eyes in myriad ways, from causing wrinkles to causing cancer, so it’s crucial to get lenses that provide 100 percent UV protection. Whether you’re buying designer shades or a cheapo pair on the street, they should have stickers on them saying they block UV. Price is no measure of safety—even fancy frames can have poor-quality lenses that block some of the light with their color but don’t absorb harmful UV radiation. That can actually make things worse: By making things darker, they cause your pupils to dilate (open wider), inviting even more radiation into the eye itself. If you’re not sure about your sunglasses, get them tested by an eye care professional.

MORE: How to Choose the Best Sunglasses