Young Brunette Girl With Sunglasses Reveals On The Field

Clear lenses are typically used to protect the eyes from impact, debris, dust, or chemicals. Some sunglasses with interchangeable lens have wet lenses to protect the eyes during low light or early morning activities.
While some blue blocking sunglasses are produced as regular sunglasses for exposure to bright sunlight, others—especially for macular degeneration patients—do not block light or other colors in order to function well in regular daylight and even dim sunlight. The latter allow the passage of enough light so normal evening activities can continue, while blocking the light that prevents production of the hormone melatonin. Low-blue tinted glasses are sometimes recommended to treat insomnia; they are worn in artificial lighting after dark, to reestablish the circadian rhythm.
Some models have polarized lenses, made of Polaroid polarized plastic sheeting, to reduce glare caused by light reflected from polarizing surfaces such as water (Brewster's angle) as well as by polarized diffuse sky radiation (skylight). This can be especially useful when fishing, for which the ability to see beneath the surface of the water is crucial.
A mirrored coating can also be applied to the lens. This mirrored coating deflects some of the light when it hits the lens so that it is not transmitted through the lens, making it useful in bright conditions; however, it does not necessarily reflect UV radiation as well. Mirrored coatings can be made any color by the manufacturer for styling and fashion purposes. The color of the mirrored surface is irrelevant to the color of the lens. For example, a gray lens can have a blue mirror coating, and a brown lens can have a silver coating. Sunglasses of this type are sometimes called mirrorshades. A mirror coating does not get hot in sunlight and it prevents scattering of rays in the lens bulk.