Glasses, sunglasses or eyeglasses are frames bearing lenses bring before the eyes normally for vision correction or eye protection or for protection from UV rays. Special glasses are used to display images in three dimensions from two-dimensional displays or experiencing virtual reality.
Modern glasses are typically supported by pads on the bridge of the nose and by temples placed over the ears. Historical rates are the glasses, monocle, and lorgnette.Glasses frames are commonly made of metal, horn or plastic. Lenses were originally made of glass, but many are now made from various types of plastic. These materials reduce the danger of breakage and weigh less than glass lenses. Some plastics also have more advantageous optical properties than glass like better transmission of visible light and greater absorption of ultraviolet light. Some plastics have a higher index of refraction than most types of glass, which is useful in the manufacture of corrective lenses shaped to correct vision abnormalities such as myopia, allowing thinner lenses for a particular recipe.
Scratch-resistant coatings can be applied to most plastic lenses giving them similar scratch resistance to glass. Hydrophobic coatings designed to ease cleaning are also available, as well as anti-reflective coatings to improve night vision and make the user’s eyes more visible.
Some crystals are not designed to correct vision. Safety glasses are a kind of eye protection against debris or against the visible and near visible light or radiation. Sunglasses allow better vision in daylight, and may protect against damage from high levels of ultraviolet light. Some crystals are also designed solely for aesthetic values, or values of fashion.
