Eyeglasses (U.S), glasses or spectacles (also more rarely cheaters) are pieces of glass or clear plastic, called lenses, that are held in front of a person's eyes by a frame made of metal or plastic.
They can be used for many reasons. These include safety, fashion and to correct a person's vision. The earliest known eyeglasses are in the thirteenth century in Italy.
Corrective lenses let some people see or read better if they have problems seeing. If the someone is long-sighted (the light is focusses past the retina), they use a different type of glasses than someone who is short-sighted. Lenses can also correct Astigmatism. Contact lenses also help people see better. Corrective lenses usually are made by opticians following eyeglass prescription from an optometrist. It's also possible to get adjustable focus glasses where one can change the lens power.
Reading glasses that are sold over the counter may help those with presbyopia who only need to wear glasses occasionally. They typically come in lens powers from +0.25 to +4.
3d glasses are used during 3d movies.
Glasses can also protect the eyes. Goggles and safety glasses are strong and protect the eyes from flying objects. Sunglasses (with dark tinted lenses) keep too much sunlight from getting in people's eyes. Some glasses are tinted for special applications, fashion and light sensitivity conditions. Some eyeglasses, often with yellow lenses, block blue light from a computer, game, tablet, smart phone or TV.
Eyeglasses are made in many different styles. These may be worn for fashion or function. These styles include:
Historical styles
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