Cycling glasses

the sun — mainly they keep wind, insects and small stones from the wheels ahead of you out of your eyes, and so they are useful even when it's cloudy. The lens category tells you how much light they let through: dark for bright sun, clear or yellow for dusk and the forest. Photochromic lenses adjust themselves and sort out the ride from the woods to the fields. The curved shape provides coverage from the sides too. Ventilation at the top edge helps prevent fogging, as does taking the glasses off your forehead when you stop.