Sunday, June 6, 2010

Eye Glasses


Glasses, spectacles, or eyeglasses are frames-bearing lenses worn in front of the eyes normally for vision correction or eye protection or for protection from UV rays. Special glasses are used for viewing three-dimensional images 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 types include the pince-nez, monocle, and lorgnette.Glasses frames are commonly made from metal, horn or plastic. Lenses were originally made from glass, but many are now made from various types of plastic.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, such as better transmission of visible light and greater absorption of ultraviolet light. Some plastics have a greater index of refraction than most types of glass; this is useful in the making of corrective lenses shaped to correct vision abnormalities such as myopia, allowing thinner lenses for a given prescriptionScratch-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 are anti-reflective coatings intended to improve night vision and make the wearer's eyes more visible.
Some glasses are not designed for vision correction. Safety glasses are a kind of eye protection against flying debris or against visible and near visible light or radiation. Sunglasses allow better vision in bright daylight, and may protect against damage from high levels of ultraviolet light. Some glasses are also designed purely for aesthetic values, or for fashion values.

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