Sunglasses 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.
Many people find direct sunlight too bright to be comfortable, especially when reading from paper in direct sunlight. In outdoor activities like riding, skiing and flying, the eye can receive more light than usual. It has been recommended to wear these kind of glasses whenever outside to protect the eyes from ultraviolet radiation, which can lead to the development of a cataract. Sunglasses have also been associated with celebrities and film actors primarily due to the desire to mask identity, but in part due to the lighting involved in production typically being stronger than natural light and uncomfortable to the naked eye.
Since the 1950s sunglasses have been popular as a fashion statement, especially on the beach.
Excessive exposure to ultraviolet radiation (UV) can cause short-term and long-term ocular problems such as photokeratitis, snow blindness, cataracts, pterygium, and various eye cancers.[2] Medical experts often advise the public on the importance of wearing sunglasses to protect the eyes from UV[2]. In the European Union, a CE mark identifies glasses fulfilling quality regulations. In the preparation for solar eclipses, health authorities often warn against looking at the sun through sunglasses alone.
There is no demonstrated correlation between high prices and increased UV protection. A 1995 study reported that "Expensive brands and polarizing sunglasses do not guarantee optimal UVA protection." [3] The Australian Competition and Consumer Commission has also reported that "[c]onsumers cannot rely on price as an indicator of quality".[4] One unscientific survey even found a $6.95 pair of generic glasses with slightly better protection than Salvatore Ferragamo shades.[5]
More recently, High energy visible light (HEV) has been implicated as a cause of age-related macular degeneration[6][7], and some manufacturers design to block it. Sunglasses may be especially important for children, as their ocular lenses are thought to transmit far more HEV light than adults (lenses "yellow" with age).
Some sunglasses also pass ANSI Z87.1 requirements for basic impact and high impact protection. These are voluntary standards, so not all sunglasses comply, nor are manufacturers required to comply. In the basic impact test, a 1 in (2.54 cm) steel ball is dropped on the lens from 50 in (127 cm). In the high velocity test, a 1/4 in (6.35mm) steel ball is shot at the lens at 150 ft/s (45.72 m/s). In both tests, no part of the lens can touch the eye.