Squinting at the sun—or even your phone or computer—forces the muscles between your brows and around your eyes to contract, which causes the overlying skin to crease. “Initially you may see the wrinkle only when you make the movement, but over time the collagen will break down and the wrinkles will become deeper and fixed,” says Dr. Shah. The most common symptom of squinting? Crow’s feet! The best way to prevent them is to wear sunglasses.