Sunglasses or sun glasses are a visual aid, variously termed spectacles or glasses, which feature lenses that are coloured or darkened to prevent strong light from reaching the eyes. In the early Twentieth century they were also known as sun cheaters (or simply cheaters). 
Many people find direct sunlight too bright to be comfortable. During outdoor activities, the human eye can receive more light than usual. Healthcare professionals recommend eye protection whenever outside to protect the eyes from ultraviolet radiation, which can lead to the development of a cataract. Sunglasses have long been associated with celebrities and film actors primarily from a desire to hide or mask their identity. Since the 1940s sunglasses have been popular as a fashion accessory, especially on the beach.
Many people find direct sunlight too bright to be comfortable. During outdoor activities, the human eye can receive more light than usual. Healthcare professionals recommend eye protection whenever outside to protect the eyes from ultraviolet radiation, which can lead to the development of a cataract. Sunglasses have long been associated with celebrities and film actors primarily from a desire to hide or mask their identity. Since the 1940s sunglasses have been popular as a fashion accessory, especially on the beach.
History
It is said that the Roman emperor Nero liked to watch gladiator fights with emeralds. These, however, appear to have worked rather like mirrors. Flat panes of smoky quartz which offered no corrective powers but did protect the eyes from glare were used in China in the 12th century or possibly earlier. Contemporary documents describe the use of such crystals by judges in Chinese courts to conceal their facial expressions while questioning witnesses.
James Ayscough began experimenting with tinted lenses in spectacles in the mid-18th century. These were not "sunglasses" as such; Ayscough believed blue- or green-tinted glass could correct for specific vision impairments. Protection from the sun's rays was not a concern of his.
It is said that the Roman emperor Nero liked to watch gladiator fights with emeralds. These, however, appear to have worked rather like mirrors. Flat panes of smoky quartz which offered no corrective powers but did protect the eyes from glare were used in China in the 12th century or possibly earlier. Contemporary documents describe the use of such crystals by judges in Chinese courts to conceal their facial expressions while questioning witnesses.
James Ayscough began experimenting with tinted lenses in spectacles in the mid-18th century. These were not "sunglasses" as such; Ayscough believed blue- or green-tinted glass could correct for specific vision impairments. Protection from the sun's rays was not a concern of his.
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