There is no universal standard for labeling sunglasses, so you may want to talk to your eye care provider about which sunglasses he or she recommends. If you are outdoors a lot, you may want to wear wrap-around glasses, which protect your eyes from the sides. Polarized lenses reduce glare from other surfaces, such as water or snow. However, they don't block UV light unless they are combined with a UV-blocking coating. Mirror coatings alone do not provide UV protection and should be combined with a UV-blocking coating.
Photochromic lenses change their degree of darkness in response to lighting conditions.
They are almost clear in low light and become darkly tinted in bright light. If you are considering photochromic lenses, ask your eye care provider if they block UV light. Experts recommend that anyone who is going to be out in the sun long enough to burn or tan should wear UV-blocking sunglasses. Recently, researchers have found that the global ozone layer is thinner than it used to be, and more UV rays are reaching the earth. Developed by McKessonHBOC Clinical Reference Systems.