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).[1]
Many people find direct sunlight too bright for comfort during outdoor activities. Healthcare professionals recommend eye protection whenever the sun comes out[2] 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.
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In prehistoric and historic time, Inuit peoples wore flattened walrus ivory "glasses," looking through narrow slits to block harmful reflected rays of the sun.[3]
It is said that the Roman emperor Nero liked to watch gladiator fights with emeralds. These, however, appear to have worked rather like mirrors.[4] 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.[5]
James Ayscough began experimenting with tinted lenses in spectacles in the mid-18th century, around 1752. These were not "sunglasses" as that term is now used; Ayscough believed blue- or green-tinted glass could correct for specific vision impairments. Protection from the Sun's rays was not a concern for him.
Yellow/amber and brown-tinted spectacles were also a commonly prescribed item for people with syphilis in the 19th and early 20th centuries because sensitivity to light was one of the symptoms of the disease.
In the early 1900s, the use of sunglasses started to become more widespread, especially among stars of movies. It is commonly believed that this was to avoid recognition by fans, but an alternative reason sometimes given is that they often had red eyes from the powerful arc lamps that were needed due to the extremely slow speed film stocks used. The stereotype persisted long after improvements in film quality and the introduction of ultraviolet filters had eliminated this problem. Inexpensive mass-produced sunglasses were introduced to America by Sam Foster in 1929. Foster found a ready market on the beaches of Atlantic City, New Jersey, where he began selling sunglasses under the name Foster Grant from a Woolworth on the Boardwalk.
Polarized sunglasses first became available in 1936, when Edwin H. Land began experimenting with making lenses with his patented Polaroid filter.
Sunglasses can improve visual comfort and visual clarity by protecting the eye from glare.[6]
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.
Sunglasses offer protection against excessive exposure to light, including its visible and invisible components.
The most widespread protection is against ultraviolet radiation, which can cause short-term and long-term ocular problems such as photokeratitis, snow blindness, cataracts, pterygium, and various forms of eye cancer.[7] Medical experts advise the public on the importance of wearing sunglasses to protect the eyes from UV;[7] for adequate protection, experts recommend sunglasses that reflect or filter out 99-100 % of UVA and UVB light, with wavelengths up to 400 nm. Sunglasses which meet this requirement are often labeled as "UV400." This is slightly more protection than the widely used standard of the European Union (see below), which requires that 95 % of the radiation up to only 380 nm must be reflected or filtered out.[8] Sunglasses are not sufficient to protect the eyes against permanent harm from looking directly at the Sun, even during a solar eclipse.
More recently, high-energy visible light (HEV) has been implicated as a cause of age-related macular degeneration;[9] before, debates had already existed as to whether "blue blocking" or amber tinted lenses may have a protective effect.[10] Some manufacturers already design to block blue light; the insurance company Suva, which covers most Swiss employees, asked eye experts around Charlotte Remé (ETH Zürich) to develop norms for blue blocking, leading to a recommended minimum of 95% of the blue light.[8][11] Sunglasses are especially important for children, as their ocular lenses are thought to transmit far more HEV light than adults (lenses "yellow" with age).
There has been some speculation that sunglasses actually promote skin cancer.[12] This is due to the eyes being tricked into producing less melanocyte-stimulating hormone in the body.
The only way to assess the protection of sunglasses is to have the lenses measured, either by the manufacturer or by a properly equipped optician. Several standards for sunglasses (see below) allow a general classification of the UV protection (but not the blue light protection), and manufacturers often indicate simply that the sunglasses meet the requirements of a specific standard rather than publish the exact figures.
The only "visible" quality test for sunglasses is their fit. The lenses should fit close enough to the face that only very little "stray light" can reach the eye from their sides, or from above or below, but not so close that the eyelashes smear the lenses. To protect against "stray light" from the sides, the lenses should fit close enough to the temples and/or merge into broad temple arms or leather blinders.
It is not possible to "see" the protection that sunglasses offer. Dark lenses do not automatically filter out more harmful UV radiation and blue light as compared to light lenses. Inadequate dark lenses are even more harmful than inadequate light lenses (or wearing no sunglasses at all) because they provoke the pupil to open wider. As result, more unfiltered radiation enters the eye. Depending on the manufacturing technology, sufficiently protective lenses can block much or little light, resulting in dark or light lenses. The lens color is not a guarantee either. Lenses of various colors can offer sufficient (or insufficient) UV protection. Regarding blue light, the color gives at least a first indication: Blue blocking lenses are commonly yellow or brown whereas blue or gray lenses cannot offer the necessary blue light protection. However, not every yellow or brown lens blocks sufficient blue light. In rare cases, lenses can filter out too much blue light (i.e., 100 %), which affects color vision and can be dangerous in traffic when colored signals are not properly recognized.
High prices cannot guarantee sufficient protection as no correlation between high prices and increased UV protection has been demonstrated. A 1995 study reported that "Expensive brands and polarizing sunglasses do not guarantee optimal UVA protection."[13] The Australian Competition and Consumer Commission has also reported that "[c]onsumers cannot rely on price as an indicator of quality".[14] One survey even found that a $6.95 pair of generic glasses offered slightly better protection than did expensive Salvatore Ferragamo shades.[15]
While non-tinted glasses are very rarely worn without the practical purpose of correcting eyesight or protecting one's eyes, sunglasses have become popular for several further reasons, and are sometimes worn even indoors or at night.
Sunglasses can be worn to hide one's eyes. They can make eye contact impossible, which can be intimidating to those not wearing sunglasses; the avoided eye contact can also demonstrate the wearer's detachment, which is considered desirable ("cool") in some circles. Eye contact can be avoided even more effectively by using mirrored sunglasses. Sunglasses can also be used to hide emotions; this can range from hiding blinking to hiding weeping and its resulting red eyes. In all cases, hiding one's eyes has implications for nonverbal communication.
Fashion trends can be another reason for wearing sunglasses, particularly designer sunglasses, but not always. Sunglasses of particular shapes may be in vogue as a fashion accessory. Fashion trends can also draw on the "cool" image of sunglasses.
People may also wear sunglasses to hide an abnormal appearance of their eyes. This can be true for people with severe visual impairment, such as the blind, who may wear sunglasses to avoid making others uncomfortable. The assumption is that it may be more comfortable for another person not to see the hidden eyes rather than see abnormal eyes or eyes which seem to look in the wrong direction. People may also wear sunglasses to hide dilated or contracted pupils, bloodshot eyes due to drug use, recent physical abuse (such as a black eye), exophthalmos (bulging eyes), a cataract, or eyes which jerk uncontrollably (nystagmus).
There are three major sunglass standards, which are popularly known mostly as a reference for sunglass protection from UV radiation; the standards do, however, also include further requirements. A worldwide ISO standard does not yet exist, but by 2004, attempts to introduce such standard have led to a respective ISO standards committee, subcommittee, technical committee, and several working groups.[16] Sunglasses sold in the United States are regulated by the Food and Drug Administration and are required to conform to safety standards.
The Australian Standard is AS/NZS 1067:2003 Sunglasses and fashion spectacles. The five ratings for transmittance (filter) under this standard are based on the amount of absorbed light, 0 to 4, with "0" providing some protection from UV radiation and sunglare, and "4" indicating a high level of protection, but not to be worn when driving. Australia introduced the world's first national standards for sunglasses in 1971. They were subsequently updated and expanded, leading in 1990 to AS 1067.1-1990 Sunglasses and fashion spectacles (incl. Part 1 Safety Requirements and Part 2 Performance Requirements), which was superseded in part in 2003 by AS/NZS 1067:2003 Sunglasses and fashion spectacles. The 2003 update made the Australian standard relatively similar to the European standard. This step opened the European market to Australian-made sunglasses, but the standard also maintained requirements considered specific to Australia's climate.[17]
The European standard EN 1836:2005 has four transmittance ratings: "0" for insufficient UV protection, "2" for sufficient UHV protection, "6" for good UHV protection and "7" for "full" UHVV protection, meaning that no more than 5 % of the 380 nm rays are transmitted. Products which fulfill the standard receive a CE mark. There is no rating for transmittance protection for radiation of up to 400 nm ("UV400"), as required in other countries (incl. the United States) and recommended by experts.[8] The current standard EN 1836:2005 was preceded by the older standards EN 166:1995 (Personal eye protection –Specifications), EN167: 1995 (Personal eye protection – Optical test methods), and EN168: 1995 (Personal eye protection – Non-optical test methods), which in 2002 were republished as a revised standard under the name of EN 1836:1997 (which included two amendments). In addition to filtering, the standard also lists requirements for minimum robustness, labeling, materials (non-toxic for skin contact and not combustible) and lack of protrusions (to avoid harm when wearing them).[16]
The U.S. standard is ANSI Z80.3-2001, which includes three transmittance categories. According to the ANSI Z80.3-2001 standard, the lens should have a UVB (280 to 315 nm) transmittance of no more than one per cent and a UVA (315 to 380 nm) transmittance of no more than 0.3 times the visual light transmittance. The ANSI Z87.1-2003 standard includes requirements for basic impact and high impact protection. In the basic impact test, a 1 in (2.54 cm) steel ball is dropped on the lens from a height of 50 in (127 cm). In the high velocity test, a 1/4 in (6.35 mm) steel ball is shot at the lens at 150 ft/s (45.72 m/s). To pass both tests, no part of the lens may touch the eye. [17]
As do corrective glasses, sunglasses have to meet special requirements when worn for sports. They need shatterproof and impact-resistant lenses; a strap or other fixing is typically used to keep glasses in place during sporting activities, and they have a nose cushion.
For water sports, so-called water sunglasses (also: surf goggles or water eyewear) are specially adapted for use in turbulent water, such as the surf or whitewater. In addition to the features for sports glasses, water sunglasses can have increased buoyancy to stop them from sinking should they come off, and they can have a vent or other method to eliminate fogging. These sunglasses are used in water sports such as surfing, windsurfing, kiteboarding, wakeboarding, kayaking, jet skiing, bodyboarding, and water skiing.
Mountain climbing or traveling across glaciers or snowfields requires above-average eye protection, because sunlight (including ultraviolet radiation) is more intense in higher altitudes, and snow and ice reflect additional light. Popular glasses for this use are a type called glacier glasses or glacier goggles. They typically have very dark round lenses and leather blinders at the sides, which protect the eyes by blocking the Sun's rays around the edges of the lenses.
Special protection is required for space travel because the sunlight is far more intense and harmful than on Earth, where it is always filtered through the atmosphere. Sun protection is needed against much higher UV radiation and even against harmful infrared radiation, both within and outside the spacecraft. Within the spacecraft, astronauts wear sunglasses with darker lenses and a thin protective gold coating. During space walks, the visor of the astronauts' helmets, which also has a thin gold coating for extra protection, functions as strong sunglasses.[18][19][20] Also the frames of glasses in space need to satisfy special requirements. Similar to sports glasses, they should be flexible and durable, and have a reliable fit that can withstand zero-gravity conditions. Some astronauts wear glasses underneath tight helmets and in their space suits, which requires a specially well-fitting frame: Once inside the spacesuit, they cannot touch their heads to push slipped glasses back into place, sometimes for a duration of up to 10 hours while working in zero-gravity. Another risk is that small pieces (screws, glass particles) of the glasses may dislodge and then float into an astronaut's respiratory system. While some of these challenges, especially wearing glasses inside a sunlight-protected spacesuit helmet, may relate to corrective glasses and not necessarily to sunglasses, today NASA uses the same frames for both types of glasses, so that the frames have to withstand all conditions. A related challenge is that even astronauts who do not wear glasses on Earth use corrective glasses in space because zero-gravity and pressure changes temporarily affect their vision; this results in 90 % of astronauts wearing glasses in space, as opposed to 70 % on Earth.[18]
The first sunglasses used in a Moon landing were the original Pilot Sunglasses produced by American Optical. In 1969, they were on board the Eagle, the lunar landing module of the first manned mission to land on the Moon (Apollo 11).[21] – NASA research primarily by scientists James B. Stephens and Charles G. Miller at the Jet Propulsion Laboratory (JPL) resulted in special lenses that protected against the light in space or the light during laser and welding work. The lenses used colored dyes and small zinc oxide particles; zinc oxide absorbs ultaviolet light and is also used in sunscreen lotions. The research was later broadened to further terrestrial applications, e.g., deserts, mountains, or fluorescent-lighted offices, and the technology has been commercially marketed by a U.S. company.[22] Since 2002, NASA uses the frame of the designer model Titan Minimal Art of the Austrian company Silhouette, combined with specially dark lenses developed jointly by the company and "the" NASA optometrist Keith Manuel. The frame is noteworthy in that it is very light, weighing 1.8 grams, and contains neither screws nor hinges, so that no small pieces can loosen.[18]
The color of the lens can vary depending on style, fashion, and purpose, but for general use, red, grey, green, or brown are recommended to avoid or minimize color distortion, which could affect safety when, for instance, driving a car or a school bus.
With the introduction of office computing, ergonomists may recommend mildly tinted glasses for use by display operators, in order to increase contrast.
While some blue blocking sunglasses (see above) are produced as regular sunglasses for exposure to bright sunlight, others—especially for macular degeneration patients—do not block light or other colors in order to function well in regular daylight and even dim sunlight.[8] The latter allow the passage of enough light so normal evening activities can continue, while blocking the light that prevents production of the hormone melatonin. Blue-blocking tinted glasses, i.e. amber or yellow, are sometimes recommended to treat insomnia; they are worn in artificial lighting after dark, to reestablish the circadian rhythm.
Some models have polarized lenses, made of Polaroid polarized plastic sheeting, to reduce glare caused by light reflected from polarizing surfaces such as water (see Brewster's angle for how this works) as well as by polarized diffuse sky radiation (skylight). This can be especially useful when fishing, for which the ability to see beneath the surface of the water is crucial.
A mirrored coating can also be applied to the lens. This mirrored coating deflects some of the light when it hits the lens so that it is not transmitted through the lens, making it useful in bright conditions; however, it does not necessarily reflect UV radiation as well. Mirrored coatings can be made any color by the manufacturer for styling and fashion purposes. The color of the mirrored surface is irrelevant to the color of the lens. For example, a gray lens can have a blue mirror coating, and a brown lens can have a silver coating. Sunglasses of this type are sometimes called mirrorshades. A mirror coating does not get hot in sunlight and it prevents scattering of rays in the lens bulk.
Sunglass lenses are made of either glass, plastic, or SR-91. Plastic lenses are typically made from acrylic, polycarbonate, CR-39 or polyurethane. Glass lenses have the best optical clarity and scratch resistance, but are heavier than plastic lenses. They can also shatter or break on impact. Plastic lenses are lighter and shatter-resistant, but are more prone to scratching. Polycarbonate plastic lenses are the lightest, and are also almost shatterproof, making them good for impact protection. CR-39 is the most common plastic lens, due to low weight, high scratch resistance, and low transparency for ultraviolet and infrared radiation. SR-91 is a proprietary material that was introduced by Kaenon Polarized in 2001. It exhibits all of the benefits of the other lens materials without the flaws. Kaenon's unique lens formulation was the first non-polycarbonate material to pass the high-mass impact ANSI Z.87.1 testing.[23] Additionally, it was the first to combine this passing score with the highest marks for lens clarity.
Any of the above features, color, polarization, gradation, mirroring, and materials, can be combined into the lens for a pair of sunglasses. Gradient glasses are darker at the top of the lens where the sky is viewed and transparent at the bottom. Corrective lenses or glasses can be manufactured with either tinting or darkened to serve as sunglasses. An alternative is to use the corrective glasses with a secondary lenses such as oversize sunglasses that fit over the regular glasses, clip-on lens that are placed in front of the glasses, and flip-up glasses which feature a dark lens that can be flipped up when not in use (see below). Photochromic lenses gradually darken in bright light.
Frames are generally made of plastic, nylon, a metal or a metal alloy. Nylon frames are usually used in sports because they are lightweight and flexible. They are able to bend slightly and return to their original shape instead of breaking when pressure is applied to them. This flex can also help the glasses grip better on the wearer's face. Metal frames are usually more rigid than nylon frames, thus they can be more easily damaged when the wearer participates in sport activities, but this is not to say that they cannot be used for such activities. Because metal frames are more rigid, some models have spring loaded hinges to help them grip the wearer's face better. The end of the resting hook and the bridge over the nose can be textured or have rubber or plastic material to improve hold. The ends of the resting hook are usually curved so that they wrap around the ear; however, some models have straight resting hooks. Oakley, for example, has straight resting hooks on all their glasses, preferring to call them "earstems".
Frames can be made to hold the lenses in several different ways. There are three common styles: full frame, half frame, and frameless. Full frame glasses have the frame go all around the lenses. Half frames go around only half the lens; typically the frames attach to the top of the lenses and on the side near the top. Frameless glasses have no frame around the lenses and the ear stems are attached directly to the lenses. There are two styles of frameless glasses: those that have a piece of frame material connecting the two lenses, and those that are a single lens with ear stems on each side.
Some sports-optimized sunglasses have interchangeable lens options. Lenses can be easily removed and swapped for a different lens, usually of a different colour. The purpose is to allow the wearer to easily change lenses when light conditions or activities change. The reasons are that the cost of a set of lenses is less than the cost of a separate pair of glasses, and carrying extra lenses is less bulky than carrying multiple pairs of glasses. It also allows easy replacement of a set of lenses if they are damaged. The most common type of sunglasses with interchangeable lenses has a single lens or shield that covers both eyes. Styles that use two lenses also exist, but are less common.
Nose bridges provide support between the lens and the face. They also prevent pressure marks caused by the weight of the lens or frame on the cheeks. People with large noses may need a low nose bridge on their sunglasses. People with medium noses may need a low or medium nose bridge. People with small noses may need sunglasses with high nose bridges to allow clearance.
Aviator sunglasses feature oversize teardrop-shaped lenses and a thin metal frame. The design was introduced in 1936 by the American Optical Eyewear company for issue to U.S. military aviators. As a fashion statement, aviator sunglasses are often made in mirrored, colored, and wrap-around styles.
In addition to pilots, Aviator-style sunglasses gained popularity with young people in the late 1960s and continue to be popular, with only a brief fall in demand during the 1990s.
Clip-on glasses are a form of tinted glasses that can be clipped on to eyeglasses for protection from the Sun. The best protection is polarized lens with 1.1mm. An alternative are flip-up glasses.
Gradient lenses go from a darker shade at the top to a lighter one at the bottom, so there will be more protection from sunlight the higher one looks through the lens, but the lower one looks through the lens, the less protection is offered. An advantage is that one can wear them indoors without fear of tripping over something and also allowing the user to see. Wearing sunglasses to nightclubs has become common in recent times, where the gradient lens comes in handy. Gradient lenses may also be advantageous for activities such as flying airplanes and driving automobiles, as they allow the operator a clear view of the instrument panel, low in his line of sight and usually hidden in shadow, while still reducing glare from the view out the windscreen. The Independent (London), has also referred to these style of sunglasses as the Murphy Lens.[24]
Double gradient lenses are dark at the top, light in the middle and dark at the bottom.
Gradients should not be confused with bifocals and progressive lenses.
Flip-up sunglasses add the benefits of sunglasses to corrective eyeglasses, allowing the wearer to flip up the tinted lenses for indoor use. An alternative are clip-on glasses.
Mirrored lenses, having a metallic, partially reflective coating on the outer surface, combined with a tinted glass lens, are an alternative to polarization for UV protection, improving contrast when depth perception is important such as seeing moguls and ice while skiing or snowboarding. The mirrored lens reflects glare to protect the eyes, but improves the ability to see contrasts, and mirrored lenses of different colors can expand the range of fashion styles. Their popularity with police officers in the United States has earned them the nickname "cop shades". The two most popular styles are dual lenses set in metal frames (which are often confused with Aviators, see above) and "Wraparounds" (see below).
Oversized sunglasses, which were fashionable in the 1980s, are now often used for humorous purposes. They usually come in bright colors with colored lenses and can be purchased cheaply.
The singer Elton John sometimes wore oversized sunglasses on stage in the mid-1970s as part of his Captain Fantastic act.
In the early twenty-first century moderately oversized sunglasses have become a fashion trend. There are many variations, such as the "Onassis", discussed below, and Dior white sunglasses.
Onassis glasses or "Jackie O's" are very large sunglasses worn by women. This style of sunglasses is said to mimic the kind most famously worn by Jacqueline Kennedy Onassis in the 1960s. The glasses continue to be popular with women, and celebrities may use them, ostensibly to hide from paparazzi.
Oversized sunglasses also offer more protection from sunburn due to the larger areas of skin they cover, although sunblock should still be used.
Shutter Shades were a fad in the early 1980s. Instead of tinted lenses, they decrease sun exposure by means of a set of parallel, horizontal shutters (like a small window shutter). Analogous to Inuit goggles (see above), the principle is not to filter light, but to decrease the amount of sun rays falling into the wearer's eyes. To provide UV protection, Shutter Shades sometimes use lenses in addition to the shutters; if not, they provide very insufficient protection against ultraviolet radiation and blue light.
"Teashades" (sometimes also called "John Lennon glasses", "Ozzy Glasses", after Ozzy Osbourne or, occasionally, "Granny Glasses") were a type of psychedelic art wire-rim sunglasses that were often worn, usually for purely aesthetic reasons, by members of the 1960s counterculture, as well as by opponents of segregation. Pop icons such as Mick Jagger, Roger Daltrey, John Lennon, Jerry Garcia, Boy George, Liam Gallagher and Ozzy Osbourne, all wore teashades. The original teashade design was made up of medium-sized, perfectly round lenses, supported by pads on the bridge of the nose and a thin wire frame. When teashades became popular in the late 1960s, they were often elaborated: Lenses were elaborately colored, mirrored, and produced in excessively large sizes, and with the wire earpieces exaggerated. A uniquely-colored or darkened glass lens was usually preferred. Modern versions tend to have plastic lenses, as do many other sunglasses. Teashades are hard to find in shops today; however, they can still be found at many costume Web sites and in some countries.
The term has now fallen into disuse, although references can still be found in literature of the time. "Teashades" was also used to describe glasses worn to hide the effects of marijuana (conjunctival injection) or bloodshot eyes or the effects of opiates such as heroin (pupillary constriction).
The glasses worn by Seraph in the Matrix films are teashades. Teashades are briefly referenced during a police training seminar in Hunter S. Thompson's novel Fear and Loathing in Las Vegas. Mickey Knox in Natural Born Killers wears red teashades. Lara Croft from the video-game Tomb Raider is seen wearing Teashade sunglasses. Vash the Stampede (Trigun) wears yellow-lens teashades. The iconic sunglasses of Spider Jerusalem are a variation of teashades. Jean Reno wears black teashades in the movie Léon(The Professional). Main character of Hellsing, Alucard, wears red-lensed teashades. Recently, actress and fashion icon Mary-Kate Olsen and pop music singer Lady Gaga have been seen wearing several variations of teashades. Howard Stern was also known for wearing teashades in the early to mid 90's and never taking them off in public.
The Ray-Ban Wayfarer is a plastic-framed design for sunglasses produced by the Ray-Ban company. Introduced in 1952, the trapezoidal lenses are wider at the top than the bottom and were famously worn by James Dean and other actors. The original frames were black; frames in many different colours were later introduced.
Wraparounds are a specific design of sunglasses. They are characterized by a single, smooth, semi-circular lens that covers both eyes and much of the same area of the face covered by protective goggles. The lens is usually combined with a minimal plastic frame and single piece of plastic serving as a nosepiece. As an alternative, the glasses can have two lenses, but the design evokes the same semicircle.
There are various words referring to eyepieces with darkened lenses:
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