Why do I need to wear sunglasses?

For the same reason that you need to wear sunscreen: the sun’s ultraviolet radiation damages tissue, causing at best sunburn and dry eye, and at worst melanoma and age-related macular degeneration. Sunglasses are essentially sunscreen for your eyes. A quality UV-blocking lens doesn’t have to be expensive, but is critical for anyone spending any amount of time outdoors, whether winter or summer, bright or overcast.