Protection from the Sun
It is essential to protect your eyes outdoors—whether you are out for a short walk or spending an entire afternoon at the park. Polarized, photochromic, and tinted lenses with UV-blocking treatment – shield eyes from the sun and prevent damage caused by UV light.
Most, but not all, photochromic lenses block UV rays and also transition quickly from clear to dark when exposed to natural light, making it more comfortable for your eyes. Polarized lenses reduce surface glare from water, snow, and roadways, and are ideal for anyone spending a lot of time outdoors. A no-glare treatment applied to the back of sunglass lenses will also eliminate bright reflections when the sun is behind you.
The source of the above information is directly from: The Vision Council