UV-blocking contacts contain a UV-blocking agent. You can't tell if a contact lens has a UV blocker just by looking at it — the blocking agent is clear, so as not to disturb vision. Importantly, UV-blocking contacts are not meant to replace sunglasses. A contact lens covers only your cornea, not your entire eye. Sunglasses with UV protection can cover more of your eye and the parts of your face that surround the eye, depending on the size of the sunglasses lens. That's why contacts with UV blockers are designed to complement sunglasses use as an added protection.