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).
Most people find direct sunlight too bright for comfort during outdoor activities. Healthcare professionals recommend eye protection whenever the sun comes outbeach.
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 
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[dubious ] 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 
Visual clarity and comfort
Various types of disposable sunglasses are dispensed to patients after receiving 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.
The glare is neutralized by blocking the vertical (magnetic) components of light.
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 solar eclipse.
More recently,  Sunglasses are especially important for children, as their ocular lenses are thought to transmit far more HEV light than adults (lenses “yellow” with age).
Assessing the protection of sunglasses
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.”
Further functions of sunglasses
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 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 nystagmus).
Some lawbreakers have also been known to wear sunglasses during or after committing a crime as an aid to hiding their identities.
Standards for sunglasses
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. 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.
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. 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).
The U.S. standard is 
Sunglasses in sports
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 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.
Sunglasses in space
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 
The first sunglasses used in a Moon landing were the original 
1969 on board the Buzz Aldrin stows his sunglasses before the Moon landing
1969: Helmet visor protecting Aldrin‘s eyes on the Moon
The color distortion, which could affect safety when, for instance, driving a car or a school bus.
- Gray and green lenses are considered neutral because they maintain true colors.
- Brown lenses cause some color distortion, but also increase contrast.
- Turquoise lenses are good for medium and high light conditions, because they are good at enhancing contrast, but do not cause significant color distortion.
- Orange and yellow lenses increase both contrast and depth perception. They also increase color distortion. Yellow lenses are used by pilots, boaters, fishers, shooters, and hunters for their contrast enhancement and width perception properties.
- Blue or purple lenses are mainly cosmetic.
With the introduction of citation needed]
While some blue blocking sunglasses (see citation needed]
Some models have polarized lenses, made of 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 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, 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. Photochromic lenses gradually darken when exposed to ultraviolet light.
Frames are generally made of plastic, 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 color. 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 Bausch & Lomb 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.
Double gradient lenses are dark at the top, light in the middle and dark at the bottom.
Gradients should not be confused with 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.
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, 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.
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”, “Round Metal”, 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 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.
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, Roy Orbison and other actors and singers. The original frames were black; frames in many different colors were later introduced. There is always a silver piece on the corners as well.
Wrap-arounds (sometimes also called “Yoko Ono glasses”) 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.
Other names for sunglasses
|This section does not references or sources. (January 2010)|
There are various words referring to eyepieces with darkened lenses:
- Shades is probably the most widely used term for sunglasses in North America.
- Glares is a term popular in India if the glass is dark.
- Glints is a term for glasses originating from the “glint” that is noticeable when somebody wearing glasses moves their head.
- Sun spectacles is a term used by some opticians.
- Spekkies is a term used predominantly in southern Australia.
- Sun specs (also sunspecs) is the shortened form of sun spectacles.
- Sunglass a monocle version.
- Sun-shades can also refer to the sun-shading eyepiece-type, although the term is not exclusive to these. Also in use is the derivative abbreviation, shades.
- Dark glasses (also preceded by pair of) — generic term in common usage.
- Sunnies is Australian, South African, UK and New Zealand slang
- Smoked spectacles usually refers to the darkened eyepieces worn by blind people.
- Solar shields Usually refers to models of sunglasses with large lenses.
- Stunna shades Used as a slang term in the hyphy movement, usually referring to sunglasses with oversized lenses.
- Glecks is Scottish slang for glasses or sunglasses.
- Cooling glasses is a term used in Southern India (predominantly Kerala) and the Middle East for sunglasses.
- Oakley, Inc.
- Kaenon Polarized
- Maui Jim
- Costa Del Mar
- ic! berlin
- Randolph Engineering, Inc.
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- article by Charlotte Remé, who also developed the guidelines/norms for Switzerland:
Remé, Charlotte (1997). Lichtschutz der Augen. [Light protection for Eyes] Der informierte Arzt – Gazette Medicale, 18, pp. 243-246
- “Sunglasses Raise Risk of Cancer”. Express.co.uk. 2007-06-03. http://www.express.co.uk/posts/view/8739/Sunglasses+raise+risk+of+cancer. Retrieved 2010-05-13.
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- – Some Sunglasses Are Cheap In Price Only
- “10 most wanted bank robbery suspects”. ABC Local. 2012-09-19. http://abclocal.go.com/ktrk/gallery?id=8816697&photo=2. Retrieved 2012-11-26. “In each of the instances, the female suspect wore a distinctive wig and sunglasses to conceal her identity.”
- no author (2002). Public eye looks over new standard for sunglasses (2002-01-20). website of Standards Australia. Retrieved 21 September 2009.
- MB Optics Safety (2006). The ANSI Z87.1-2003 standard. Retrieved 22 June 2011.
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- Welcome To Pech Optical
- Recommended Type of Sunglasses for People with Large Nose
|Wikimedia Commons has media related to: Sunglasses|
- What Makes A Good Pair Of Sunglasses by George W. Waltz 1951 Popular Science article on sunglasses and the method of mass production at that time period.
- ‘How to Choose Sunglasses for Your Face Shape'
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