The following article was sourced from a Wikipedia page at the following address: http://en.wikipedia.org/wiki/Sunglasses
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 coloured, polarized or darkened. In the early 20th century they were also known as sun cheaters (cheaters being an American slang term for glasses).
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. Its usage is mandatory immediately after some surgical procedures such as IntraLASIK 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.
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.
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.
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. By 1938 Life magazine wrote of how sunglasses were a "new fad for wear on city streets ... a favourite affectation of thousands of women all over the U.S." It stated that 20 million sunglasses were sold in the United States in 1937, but estimated that only about 25% of American wearers needed them to protect their eyes.
Polarized sunglasses first became available in 1936, when Edwin H. Land began experimenting with making lenses with his patented Polaroid filter.
Visual clarity and comfort
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 allow wearers to see into water when only surface glare would otherwise be seen, and eliminate glare from a road surface when driving into the sun.
The glare is neutralized by blocking the vertical (magnetic) components of light.
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. Medical experts advise the public on the importance of wearing sunglasses to protect the eyes from UV; 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. 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; before, debates had already existed as to whether "blue blocking" or amber tinted lenses may have a protective effect. 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. 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. This is due to the eyes being tricked into producing less melanocyte-stimulating hormone in the body.
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 colour is not a guarantee either. Lenses of various colours can offer sufficient (or insufficient) UV protection. Regarding blue light, the colour 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 colour vision and can be dangerous in traffic when coloured 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." The Australian Competition and Consumer Commission has also reported that "consumers cannot rely on price as an indicator of quality". One survey even found that a $6.95 pair of generic glasses offered slightly better protection than did expensive Salvatore Ferragamo shades.
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 (or "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; this is useful in poker, and many professional poker players wear heavily tinted glasses indoors while playing, so that it is more difficult for opponents to read tells which involve eye movement and thus gain an advantage.
Fashion trends can be another reason for wearing sunglasses, particularly designer sunglasses. 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).
Some lawbreakers have also been known to wear sunglasses during or after committing a crime as an aid to hiding their identities.
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.
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.
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 fulfil 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. 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, labelling, materials (non-toxic for skin contact and not combustible) and lack of protrusions (to avoid harm when wearing them).
Sunglasses sold in the United States are regulated by the Food and Drug Administration and are required to conform to safety standards. 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.
Land vehicle driving
The Automobile Association and the UK Federation of Manufacturing Opticians have produced guidance for selection of sunglasses for driving. Variable tint or photochromic lenses increase their optical density when exposed to UV light, reverting to their clear state when the UV brightness decreases. This makes them unsuitable for driving because car windscreens filter out UV light, which both slows and limits the reaction of the lenses; they could become too dark or too light for the conditions. Some manufacturers produce special photochromic lenses which adapt to the varying light conditions when driving. Lenses of fixed tint are graded according to the optical density of the tint; in the UK sunglasses must be labelled and show the filter category number. Lenses with light transmission less than 75% are unsuitable for night driving, and lenses with light transmission less than 8% (category 4) are unsuitable for driving at any time; they should by UK law be labelled 'Not suitable for driving and road use'. Yellow tinted lenses are also not recommended for night use. Due to the light levels within the car, filter category 2 lenses which transmit between 18% and 43% of light are recommended for daytime driving. Polarised lenses normally have a fixed tint, and can reduce reflected glare more than non-polarised lenses of the same density, particularly on wet roads.
Graduated lenses, with the bottom part lighter than the top, can make it easier to see the controls within the car. All sunglasses should be marked as meeting the standard for the region where sold. An anti-reflection coating is recommended, and a hard coating to protect the lenses from scratches. Sunglasses with deep side arms can block side, or peripheral, vision and are not recommended for driving.
Even though, some of these glasses are proven good enough for driving at night, it is strongly recommended not to do so, due to the changes in a wide variety of light intensities, especially, while using yellow tinted protection glasses. The main purpose of these glasses, are to protect the wearer from dust and smog particles entering into the eyes while driving at high speeds.
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 travelling 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.
The first sunglasses used in a Moon landing were the original pilot sunglasses produced by American Optical. In 1969 they were used aboard the Eagle, the lunar landing module of Apollo 11, the first manned mission to land on the Moon. 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 and during laser and welding work. The lenses used coloured dyes and small particles of zinc oxide, which absorbs ultraviolet light and is also used in sunscreen lotions. The research was later broadened to further terrestrial applications, e.g., deserts, mountains, and fluorescent-lighted offices, and the technology was commercially marketed by a U.S. company. Since 2002 NASA uses the frame of the designer model Titan Minimal Art of the Austrian company Silhouette, combined with especially dark lenses developed jointly by the company and "the" NASA optometrist Keith Manuel. The frame is very light at 1.8 grams, and does not have screws or hinges that could detach.
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 colours in order to function well in regular daylight and even dim sunlight. 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 re-establish the circadian rhythm.
Some models have polarized lenses, made of Polaroid polarized plastic sheeting, to reduce glare caused by light reflected from non-metallic 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 to see beneath the surface of the water when fishing.
A mirrored coating can 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 colour by the manufacturer for styling and fashion purposes. The colour of the mirrored surface is irrelevant to the colour 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. Kaenon's lens formulation was the first non-polycarbonate material to pass the high-mass impact ANSI Z.87.1 testing. Additionally, it was the first to combine this passing score with the highest marks for lens clarity. Jerry Garcia's sunglasses had a polykrypton-C type of lens which was 'cutting edge' in 1995.
Any of the above features, colour, 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 when exposed to ultraviolet light.
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.
The following types are not all mutually exclusive; glasses may be in Aviator style with mirrored lenses, for example.
The model first gained popularity in the 1940s when Douglas McArthur was seen sporting a pair at the Pacific Theatre. However, it was in the late 1960s when the frames became widely used with the rise of the hippie counterculture, which preferred large metallic sunglasses. The brand became an icon of the 1970s, worn by Paul McCartney and Freddie Mercury among others, and was also used as prescription eyeglasses. Aviators' association with disco culture led to a decline in their popularity by 1980. The model saw more limited use throughout the 1980s and 1990s, aided by a 1982 product placement deal, featured most notably in Top Gun and Cobra, with both films causing a 40% rise in 1986. Aviators became popular again around 2000, as the hippie movement experienced a brief revival, and was prominently featured in the MTV show Jackass.
The singer Elton John sometimes wore oversized sunglasses on stage in the mid-1970s as part of his Captain Fantastic act.
Since the late 2000s 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, because of their larger frames and lenses, are useful for individuals who are trying to minimize the apparent size or arch of their nose. Oversized sunglasses also offer more protection from sunburn due to the larger areas of skin they cover, although sunblock should still be used.
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 opiates such as marijuana (conjunctival injection) or heroin (pupillary constriction) or just bloodshot eyes.
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. Unlike the others, Jerry Garcia actually created his own line of sunglasses in his name just before he passed away.
These were mostly popular in the late 1950s and during the 1960s (being linked to the rock-and-roll/blues and Mod cultures), before plastic glasses were displaced by metallic rims popular among the counter-culture. In the late 1970s, the rise of New wave music, New Romanticism and the popularity of The Blues Brothers aside from 50s and 60s nostalgia and the anti-disco backlash later on brought the model out of near-retirement, becoming the most sold model between 1980 and 1999 aided by a lucrative 1982 product placement deal, which put it on many movies and TV shows such as The Breakfast Club and Moonlightning. 1980s nostalgia and the influence of the hipster subculture and the television series Mad Men boosted Wayfarers once again after a slump in the 1990s and 2000s, also aided by a 2000 redesign (New Wayfarer), surpassing Aviators since 2012.
These were first made in the 1960s as variants of the Aviator model, used by Yoko Ono and Clint Eastwood in the Dirty Harry films. The modern variant surged in the mid-1980s, heavily based on the then-popular Wayfarer, but adapting it to a more futuristic look. As a backlash against 80s fashion occurred in the 1990s, wraparounds became one of the favourite frames of the decade.
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.
There are various words referring to eyepieces with darkened lenses:
For more information on sunglasses, please click on the following link: http://en.wikipedia.org/wiki/Sunglasses