Sunglasses were designed to facilitate orientation and spare the eyes in an environment with strong sunlight. The Eskimos invented the primitive but effective sunglasses which only consisted of narrow slits cut in wood, bone or whale tooth with the help of which they could move about in the Arctic winter landscape without being broken.
Modern sunglasses are made typically of plastic. Sunglass lenses are tinted by which a certain portion of sunlight is absorbed before it hits your eye. Many sunglass glass contains also a polarizing filter which absorbs the horizontally polarized light. Hereby are filtered out most of the light that has been reflected in advance of secular surfaces in the landscape, for example. open water, and thus is particularly annoying.
Good sunglasses have a built-in UV filter. Corrective vision glasses are also available with sunglass effect. They can be found on internetages. Small grains of silver chloride which is embedded in the sunglasses. Brightness late appears as darkness. Silver grains seems like small mirrors and reduces the intensity of the light that passes through the glasses. In overcast skies react silver and chlorine again, and the glasses will be on the new bright.
The use of sunglasses is nowadays not only a practical item, for example skiers or a precaution taken by people with light eye color in order to avoid damage to the retina, but also a fashion object and a stylish symbol.