Shades

Sunglasses or sun glasses are a form of protective eyewear designed primarily to prevent bright sunlight and high-energy visible light from damaging or discomforting the eyes. They can sometimes also function as a visual aid, as variously termed spectacles or glasses exist, featuring lenses that are colored, polarized or darkened. In the early 20th century, they were also known as sun cheaters (cheaters being an American slang term for glasses).

The American Optometric Association recommends sunglasses whenever a person is in the sun. to protect the eyes from ultraviolet radiation (UV) and blue light, which can cause several serious eye problems. Its usage is mandatory immediately after some surgical procedures, such as LASIK, and recommended for a certain time period in dusty areas, when leaving the house and in front of a TV screen or computer monitor after LASEK. Sunglasses have long been associated with celebrities and film actors primarily from a desire to mask their identity. Since the 1940s, sunglasses have been popular as a fashion accessory, especially on the beach.

In prehistoric and historic time, Inuit peoples wore flattened walrus ivory "glasses", looking through narrow slits to block harmful reflected rays of the sun.

It is said that the Roman emperor Nero liked to watch gladiator fights with emeralds. These, however, appear to have worked rather like mirrors. Sunglasses made from 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. Ancient documents describe the use of such crystal sunglasses by judges in ancient Chinese courts to conceal their facial expressions while questioning witnesses.

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Wikipedia