The lenses of these sunglasses are coated with chemical film that helps in filtering & reducing the intensity of glare reflected from surfaces hit by sun or directly from sun. This helps reduce effects of harmful UV rays. Initially used by boaters and fishermen, these are now used by several for outdoor recreational activities like sports & driving as well as by golfers, cyclist, joggers. Not recommended while using LED and LCD screens like mobile phone, GPS as it limits its visibility. This was invented in 1929 by the founder of Polaroid corporations.