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).
Many people find direct sunlight too bright for comfort. During outdoor activities, the human eye can receive more light than usual. Healthcare professionals recommend eye protection whenever the sun comes out to protect the eyes from ultraviolet radiation (UV) and blue light, which can cause several serious eye problems. 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 the early 1900s, the use of sunglasses started to become more widespread, especially among stars of silent movies. It is commonly believed that this was to avoid recognition by fans, but the real reason was they often had perennially red eyes from the powerful arc lamps that were needed due to the extremely slow speed film stocks used.
Visual clarity and comfort
Sunglasses can improve visual comfort and visual clarity by protecting the eye from glare.
Various types of disposable sunglasses are dispensed to patients after receiving mydriatic eye drops during eye examinations.
The lenses of polarized sunglasses reduce glare reflected at some angles off shiny non-metallic surfaces such as water. They are popular among fishermen because they allow wearers to see into water when normally only glare would be seen.
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