Glasses

A pair of eyeglasses

Glasses, spectacles, or eyeglasses are frames bearing lenses worn in front of the human eyes, sometimes for purely aesthetic reasons but normally for vision correction or eye protection. Special glasses are used for viewing three-dimensional images or experiencing virtual reality.

Modern glasses are typically supported by pads on the bridge of the nose and by temples placed over the ears. Historical types include the pince nez, monocle, and lorgnette.

Glasses are more often called eyeglasses in North American English, occasionally spectacles in British English, and (rarely) frames or lenses. Spectacles is often shortened to specs. In hipster slang they are cheaters.

Glasses were originally made from glass, but many are now made from plastic (often polycarbonate or CR-39) due to the danger of breakage and the greater weight of glass lenses. Some plastics also have more advantageous optical properties than glass, such as better transmission of visible light and greater absorption of ultraviolet light. Some plastics have a greater index of refraction than most types of glass, allowing thinner lenses for a given prescription. Scratch-resistant coatings can be applied to most plastic lenses giving them similar scratch resistance to glass. Hydrophobic coatings designed to ease cleaning are also available, as are anti-reflective coatings intended to improve night vision and make the wearer's eyes more visible.

Corrective spectacles have lenses shaped to correct vision abnormalities, such as myopia.

Safety glasses are a kind of eye protection against flying debris or visible and near visible light or radiation.

Sunglasses protect against high levels of visible and ultraviolet light.

History

Detail of a portrait of Hugh de Provence, painted by Tomasso da Modena in 1352

Glasses were possibly invented in northern Italy, most likely in the late 1280s. The identity of the original inventor is unknown, although a possible source is the Arabs, who may have had magnifying lenses in the 10th century. In 1676, Franciscus Redi, a professor of medicine at the University of Pisa, wrote that he possessed a 1289 manuscript whose author complains that he would be unable to read or write were it not for the recent invention of glasses, and a record of a sermon given in 1305, in which the speaker, a Dominican monk named Fra Giordano da Rivalto, remarked that glasses had been invented less than twenty years previously, and that he had met the inventor. Based on this evidence, Redi credited another Dominican monk, Fra Alessandro da Spina of Pisa, with the re-invention of glasses after their original inventor kept them a secret, a claim contained in da Spina's obituary record. In 1738, a Florentine historian named Domenico Manni reported that a tombstone in Florence credited one Salvino d'Armato (died 1317) with the invention of glasses. Other stories, possibly legendary, credit Roger Bacon with the invention. Bacon's published writings describe the magnifying glass (which he did not invent), but make no mention of glasses.

These early spectacles had convex lenses that could correct the farsightedness (presbyopia) that commonly develops as a symptom of aging. Nicholas of Cusa is believed to have discovered the benefits of concave lens in the treatment of myopia (nearsightedness). However, it was not until 1604 that Johannes Kepler published in his treatise on optics and astronomy, the first correct explanation as to why convex and concave lenses could correct presbyopia and myopia. The American scientist Benjamin Franklin, who suffered from both myopia and presbyopia, invented bifocals in 1784 to avoid having to regularly switch between two pairs of glasses. The first lenses for correcting astigmatism were constructed by the British astronomer George Airy in 1827.

Over time, the construction of spectacle frames also evolved. Early eyepieces were designed to be either held in place by hand or by exerting pressure on the nose (pince-nez). Girolamo Savonarola suggested that eyepieces could be held in place by a ribbon passed over the wearer's head, this in turn secured by the weight of a hat. The modern style of glasses, held by temples passing over the ears, was developed in 1727 by the British optician Edward Scarlett. These designs were not immediately successful, however, and various styles with attached handles such as scissors glasses and lorgnettes remained fashionable throughout the 18th and into the early 19th century.

Despite the increasing popularity of contact lenses and laser corrective eye surgery, glasses remain very common and their technology has not stood still. For instance, it is now possible to purchase frames made of special memory metal alloys that return to their correct shape after being bent. Other frames have spring-loaded hinges. Either of these designs offers dramatically better ability to withstand the stresses of daily wear and the occasional accident.

Corrective glasses

Corrective lenses modify the focal length of the eye to alleviate the effects of shortsightedness (myopia), longsightedness (hyperopia) or astigmatism. The power of a lens is generally measured in diopters. Over-the-counter reading glasses are typically rated at +1.00 to +3.00 diopters. Glasses correcting for myopia will have negative diopter strengths. Lenses made to conform to the prescription of an ophthalmologist or optometrist are called prescription lenses and are used to make prescription glasses.

Safety glasses

Safety glasses with side shields Wraparound safety glasses

Safety glasses are usually made with shatter-resistant plastic lenses to protect the eye from flying debris. Although safety lenses may be constructed from a variety of materials that vary in impact resistance, certain standards suggest that they maintain a minimum 1mm thickness at the thinest point regardless of material. Safety glasses can vary in the level of protection they provide. For example, those used in medicine may be expected to protect against blood splatter while safety glasses in a factory might have stronger lenses and a stronger frame with additional shields at the temples. The lenses of safety glasses can also be shaped for correction. Some safety glasses are designed to fit over corrective glasses or sunglasses. They may provide less eye protection than goggles, face shields or other forms of eye protection, but their light weight increases the likelihood that they will actually be used. Recent safety glasses have tended to be given a more stylish design, in order to encourage their use. The pictured wraparound safety glasses are evidence of this style change with the close fitting nature of the wraparound dispensing with the need for side shields.

Corrective glasses with plastic lenses can often be used in the place of safety glasses in many environments; this is one advantage that they have over contact lenses.

Sunglasses

Scratch-resistant sunglasses made using a NASA developed coating

Main article: Sunglasses

Sunglasses may be made with either prescription or non-prescription (i.e. plano) lenses that are darkened to provide protection against bright visible light. Good sunglasses should also protect against ultraviolet light. Due to changes in the atmosphere, ultraviolet levels are much higher than in the past and ultraviolet protection for eyes and skin is even more important. It is possible to have lenses that look very dark and yet offer little ultraviolet protection. Sunglasses vary greatly and many offer more style than protection.

Glasses with photosensitive lenses, called photochromic lenses, become darker in the presence of UV light. Unfortunately, many car windshields protect the passengers from UV light, while not shielding from bright visible light, making photochromic lenses ineffective where they are most needed. Still, they offer the convenience of not having to carry both clear glasses and sunglasses to those who frequently go indoors and outdoors during the course of a day.

Light polarization is an added feature that can be applied to sunglass lenses. Polarization filters remove horizontal rays of light, which can cause glare. Popular among fishermen and hunters, polarized sunglasses allow wearers to see into water when normally glare or reflected light would be seen. Polarized sunglasses may present some difficulties for pilots in that reflections from water and other structures often used to gauge altitude may be removed, or instrument readings on liquid crystal displays may be blocked.

Special glasses

The illusion of three dimensions on a two dimensional surface can be created by providing each eye with different visual information. Classic 3D glasses create the illusion of three dimensions when viewing specially prepared images. The classic 3D glasses have one red lens and one blue lens. 3D glasses made of cardboard and plastic are distributed at 3D movies. Another kind of 3D glasses uses polarized filters. One kind of electronic 3D spectacles uses electronic shutters.

Virtual reality glasses and helmets have separate video screens for each eye and a method for determining the direction the head is turned.

Conditions glasses are used to correct

Glasses fitted with corrective lenses are a common means of correcting focus problems such as myopia (nearsightedness, short-sightedness) and hyperopia (farsightedness, long-sightedness). Emmetropia, the condition of ideal focus is described as two parallel rays of light entering the eye and converging on or at the retina. Myopia is a condition in which parallel rays of light entering the eye converge before reaching to retina. Hyperopia is a condition in which parallel rays of light entering the eye do not converge prior to reaching the retina. Some would say "the rays of light converge at an imaginary point behind the retina." Astigmatism is a condition in which parallel rays of light entering the eye converge at two separate locations, either before and/or after the retina. As most people age the crystalline lens of the eye loses elasticity resulting in presbyopia, which limits their ability to focus on nearby objects. None of these conditions is considered a disease.

Variation in glasses

Glasses can be very simple. Magnifying lenses for reading that are used to treat mild hypermetropia and presbyopia can be bought off the shelf, but most glasses are made to a particular prescription, based on degree of myopia or hypermetropia combined with astigmatism. Lenses can be ground to specific eyes, but in most cases standard off-the-shelf prescriptions suffice, but require custom-fitting to particular frames.

As people age, their ability to focus is lessened and many decide to use multiple-focus lenses, bifocal or even trifocal to cover all the situations in which they use their sight. Traditional multifocal lenses have two or three distinct viewing areas, each requiring a conscious effort of refocusing. These were originally separate lenses, as invented by Benjamin Franklin. Some modern multifocal lenses give a smooth transition between these lenses, unnoticeable by most wearers. Others have lenses specifically intended for use with computer monitors at a fixed distance. Many people have several pairs of glasses, one for each task or distance, with specific glasses for reading, computer use, and television watching.

Glasses as a fashion accessory

Buddy Holly's thick-rimmed glasses were part of his all-American image.

Glasses are often regarded as unattractive, and many people prefer to wear contact lenses for that reason. Contact lenses also provide much improved peripheral vision.

On the other hand, many people are attracted to people who wear glasses, and glasses are available in a wide range of styles, materials, and even designer labels.

Glasses can be a major part of personal expression, from the extravagance of Elton John and Dame Edna Everage, from Groucho Marx to John Denver to Lisa Loeb all the way to the varied professional personas of eyeglass-wearing knowledge workers.

For some celebrities, glasses form part of their identity. American Senator Barry Goldwater continued to wear lensless horn-rimmed spectacles after being fitted with contact lenses because he was not recognizable without his trademark glasses. British soap star Anne Kirkbride had the same problem: her character on Coronation Street, Deirdre Barlow, became so well-known for her big frames that she was expected to wear them at social gatherings and in international tours, even though Kirkbride has always worn contact lenses. Drew Carey continued to wear glasses for the same reason after getting corrective laser eye surgery. British comedic actor Eric Sykes, who became profoundly deaf as an adult, wears glasses that contain no lenses, but are in fact a bone-conducting hearing aid. Masaharu Morimoto wears glasses to separate his professional persona as a chef from his stage persona as Iron Chef Japanese. And of course John Lennon wore his round "granny glasses" from some of his time with the Beatles to his assassination in 1980.

In popular culture, glasses were all the disguise Superman and Wonder Woman needed to hide in plain view as alter egos Clark Kent and Diana Prince, respectively.

An example of halo effect is seen in the stereotype that those who wear glasses are intelligent or, especially in teen culture, even geeks and nerds. This conception probably comes from an era when most people were illiterate and the first people to wear glasses were those who did a lot of reading. Some people who find that wearing glasses may look nerdy turn to contact lenses instead, especially under peer pressure.

Another unpopular aspect of glasses is their inconvenience. Even though the late-20th century saw the creation of light frames, such as those made of titanium, very flexible frames, and new lens materials and optical coatings, glasses can still cause problems during rigorous sports. The lenses themselves can also become greasy or trap vapour when eating hot food or swimming or walking in rain, reducing visibility significantly. Scraping, fracturing, or breakage of the lenses require time-consuming and costly professional repair, though modern plastic lenses are almost indestructible and very scratch-resistant.

Other names for glasses

  • Pair of glasses (or just glasses) is commonly used in Britain and in North America. Compare with other meanings of the word glass.
  • Spectacles is widely used in Britain and occasionally in the US, in addition to use by professional opticians. Also in frequent use is the shortened form, specs.
  • Eye glasses or eyeglasses is a word used in North American English. In contrast, glass eye refers to a cosmetic prosthetic artificial eye that replaces a missing eye.
  • Frames is sometimes used to refer to framed eyepieces, although it is not common.
  • Lenses is also sometimes used to refer to framed eyepieces, although it is not common.
  • Cheaters is used in the hipster argot. Eyeglasses were a common part of the hipster persona, for example Dizzy Gillespie.

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Scraping, fracturing, or breakage of the lenses require time-consuming and costly professional repair, though modern plastic lenses are almost indestructible and very scratch-resistant. Hunting is central to many works by Ernest Hemingway and even used as an extended metaphor in the new age self-help fiction of Carlos Castaneda's Journey to Ixtlan. The lenses themselves can also become greasy or trap vapour when eating hot food or swimming or walking in rain, reducing visibility significantly. A favorable depiction of hunting is found in L.Neil Smith's science fiction novel Pallas. Even though the late-20th century saw the creation of light frames, such as those made of titanium, very flexible frames, and new lens materials and optical coatings, glasses can still cause problems during rigorous sports. Varmint hunting of prairie dogs is depicted in John Ross' novel Unintended Consequences. Another unpopular aspect of glasses is their inconvenience. Hunting is portrayed as necessary subsistence, as is the case in many Alaskan Bush communities today.[6].

Some people who find that wearing glasses may look nerdy turn to contact lenses instead, especially under peer pressure. The 1990 film Dances with Wolves or the 1970 Little Big Man contrast modern hunters with a romantic noble savage, and filmed depictions of hunting by aboriginal cultures like Native Americans tend to be more sympathetic. This conception probably comes from an era when most people were illiterate and the first people to wear glasses were those who did a lot of reading. Hunting may also be depicted in a matter-of-fact way, as with Gollum's fishing in Peter Jackson's adaptation of The Lord of the Rings. An example of halo effect is seen in the stereotype that those who wear glasses are intelligent or, especially in teen culture, even geeks and nerds. At the other end of the spectrum Ted Nugent portrays the hunter as a rock and roll iconoclast. In popular culture, glasses were all the disguise Superman and Wonder Woman needed to hide in plain view as alter egos Clark Kent and Diana Prince, respectively. Such anthropomorphism of prey animals or "varmints" is frequently used as social satire, with the audience intended to sympathize with the hunted animal and the socially powerful hunter portrayed as incompetent or a macho buffoon.

And of course John Lennon wore his round "granny glasses" from some of his time with the Beatles to his assassination in 1980. Some of the most widespread depictions of hunting have been through animation, particularly in movies such as the 1942 film Bambi and through Looney Tunes cartoons featuring Bugs Bunny and Elmer Fudd. Masaharu Morimoto wears glasses to separate his professional persona as a chef from his stage persona as Iron Chef Japanese.
In addition to positive portrayals of hunting and hunters on television shows aimed at hunters, hunting is also frequently portrayed in movies and popular culture as part of a broader social commentary. British comedic actor Eric Sykes, who became profoundly deaf as an adult, wears glasses that contain no lenses, but are in fact a bone-conducting hearing aid. Within American industrial forestry, deer are often considered pests, and hunters a key political ally to be used against more restrictive environmentalists. Drew Carey continued to wear glasses for the same reason after getting corrective laser eye surgery. A marginal ranch or farm may be converted to a private "hunting preserve" to bring in tourist revenues, for example.

British soap star Anne Kirkbride had the same problem: her character on Coronation Street, Deirdre Barlow, became so well-known for her big frames that she was expected to wear them at social gatherings and in international tours, even though Kirkbride has always worn contact lenses. Key parts of the agricultural industry may also support hunting. American Senator Barry Goldwater continued to wear lensless horn-rimmed spectacles after being fitted with contact lenses because he was not recognizable without his trademark glasses. The Outdoor Channel and OLN are cable television channels where programs such as Hunter's Handbook TV teach hunting safety and showcase new hunting destinations or products such as recreational vehicles, specialty clothing or firearms. For some celebrities, glasses form part of their identity. In 2001, over 13 million hunters averaged eighteen days hunting and spent over $20.5 billion on their sport. Glasses can be a major part of personal expression, from the extravagance of Elton John and Dame Edna Everage, from Groucho Marx to John Denver to Lisa Loeb all the way to the varied professional personas of eyeglass-wearing knowledge workers. Today's hunters come from a broad range of economic, social, and cultural backgrounds, including a significant luxury segment.

On the other hand, many people are attracted to people who wear glasses, and glasses are available in a wide range of styles, materials, and even designer labels. Hunting is also a major industry in the United States, with many companies specializing in hunting equipment or specialty tourism. Contact lenses also provide much improved peripheral vision. In the United Kingdom the game hunting of birds as an industry is said to be extremely important to the rural economy: The Cobham Report of 1997 suggested it to be worth around £700 million, and hunting and shooting lobby groups now claim it to be worth over a billion. Glasses are often regarded as unattractive, and many people prefer to wear contact lenses for that reason. They argue that these hunters allows for anti-poaching activities and revenue for local communities [5]. Many people have several pairs of glasses, one for each task or distance, with specific glasses for reading, computer use, and television watching. Safari hunters are also more likely to use remote areas, uninviting to the average eco-tourist.

Others have lenses specifically intended for use with computer monitors at a fixed distance. In contrast the average safari hunter travels on foot, staying in tented camps and in vastly smaller numbers. Some modern multifocal lenses give a smooth transition between these lenses, unnoticeable by most wearers. The average photo tourist demands luxury accommodations and at a higher number of visitors to make the endeavor financially viable. These were originally separate lenses, as invented by Benjamin Franklin. In Tanzania it is estimated that safari hunter spends 50-100 times that of the average eco-tourist and at a lower environmental impact. Traditional multifocal lenses have two or three distinct viewing areas, each requiring a conscious effort of refocusing. A variety of industries benefit from hunting, and support hunting on economic grounds, beyond the ecological arguments of hunter-gathering and pastoral use of marginal habitats.

As people age, their ability to focus is lessened and many decide to use multiple-focus lenses, bifocal or even trifocal to cover all the situations in which they use their sight. This along with fees paid to hunt contribute to the local economy and provide value to animals that would otherwise be seen as competition for grazing, livestock, and crops [4]. Lenses can be ground to specific eyes, but in most cases standard off-the-shelf prescriptions suffice, but require custom-fitting to particular frames. They note that modern regulations explicitly address issues of unnecessary harassment and that the vast majority of the edible portions of the animal are consumed by the hunters themselves or given to local inhabitants. Magnifying lenses for reading that are used to treat mild hypermetropia and presbyopia can be bought off the shelf, but most glasses are made to a particular prescription, based on degree of myopia or hypermetropia combined with astigmatism. Advocates of trophy hunting disagree. Glasses can be very simple. Other people also object to trophy hunting in general because it is seen as a senseless act of killing another living thing for recreation, rather than food.

None of these conditions is considered a disease. In modern times, trophy hunting persists, but is frowned upon by some when it involves rare or endangered species of animal. As most people age the crystalline lens of the eye loses elasticity resulting in presbyopia, which limits their ability to focus on nearby objects. The safari method of hunting was a development of sport hunting that saw elaborate travel in Africa, India and other places in pursuit of trophies. Some would say "the rays of light converge at an imaginary point behind the retina." Astigmatism is a condition in which parallel rays of light entering the eye converge at two separate locations, either before and/or after the retina. Hunting in North America in the 1800s was done primarily as a way to supplement food supplies. Hyperopia is a condition in which parallel rays of light entering the eye do not converge prior to reaching the retina. They see such killing as an issue of morality, citing British fox hunting as an especially inhumane "blood sport.".

Myopia is a condition in which parallel rays of light entering the eye converge before reaching to retina. Trophy hunting is the most controversial aspect of hunting for opponents of hunting, who argue that modern economics or vegetarianism should eliminate the need for most killing of animals, if not animal domestication entirely. Emmetropia, the condition of ideal focus is described as two parallel rays of light entering the eye and converging on or at the retina. This is perhaps the most common practice of modern hunters worldwide. Glasses fitted with corrective lenses are a common means of correcting focus problems such as myopia (nearsightedness, short-sightedness) and hyperopia (farsightedness, long-sightedness). In the Nordic countries, hunting for trophies was, and still is frowned upon, but an impressive trophy is considered a bonus. Virtual reality glasses and helmets have separate video screens for each eye and a method for determining the direction the head is turned. In contrast, in relatively scarcely populated northern Europe, hunting has remained the tradition of the common people, and still serves a purpose as a means of acquiring meat, although the standard of living does not require it; Eating game is generally considered a healthier and more ethical alternative to the exploitation of farmed animals.

One kind of electronic 3D spectacles uses electronic shutters. The rest of the animal was often wasted. Another kind of 3D glasses uses polarized filters. In the 1800s southern and central European hunters often pursued game only for a trophy, usually the head or pelt of an animal, to be displayed as a sign of prowess. 3D glasses made of cardboard and plastic are distributed at 3D movies. Often a hunter will use a combination of more than one technique, and some are used primarily in poaching and wildlife management, explicitly forbidden to sport hunters. The classic 3D glasses have one red lens and one blue lens. Techniques may vary depending on government regulations, a hunter's personal ethics, local custom, weapons and the animal being hunted.

Classic 3D glasses create the illusion of three dimensions when viewing specially prepared images. Historical, subsistence and sport hunting techniques can differ radically, with modern hunting regulations often addressing issues of where, when and how hunts are conducted. The illusion of three dimensions on a two dimensional surface can be created by providing each eye with different visual information. Overpopulations of deer in urban parks and bears which have attacked humans might be hunted by animal management authorities. Polarized sunglasses may present some difficulties for pilots in that reflections from water and other structures often used to gauge altitude may be removed, or instrument readings on liquid crystal displays may be blocked. These hunts are sometimes carried out by professional hunters although other hunts include amateurs. Popular among fishermen and hunters, polarized sunglasses allow wearers to see into water when normally glare or reflected light would be seen. Animal management authorities sometimes rely on hunting to control certain animal populations.

Polarization filters remove horizontal rays of light, which can cause glare. The reason for the Conservation Order is that these species have grown so numerous that they are destroying the Arctic environment which many species of animals use as breeding grounds. Light polarization is an added feature that can be applied to sunglass lenses. An example of using hunters in wildlife management can be found in the "Snow, Blue and Ross' Goose Conservation Order 2005." [3] The Conservation Order allows hunters, after all other waterfowl seasons are closed, to shoot an unlimited number of these species of geese. Still, they offer the convenience of not having to carry both clear glasses and sunglasses to those who frequently go indoors and outdoors during the course of a day. Some environmentalists assert that introducing appropriate predator animals would achieve the same benefit with more efficiency and less environmental impact, but some livestock owners disagree, seeing human killing as more explicitly selective. Unfortunately, many car windshields protect the passengers from UV light, while not shielding from bright visible light, making photochromic lenses ineffective where they are most needed. Hunting reduces the annual crop of new animals and birds to allow the remaining animals sufficient feed and shelter to survive.

Glasses with photosensitive lenses, called photochromic lenses, become darker in the presence of UV light. Hunting gives resource managers a valuable tool to control populations of some species that might otherwise exceed the carrying capacity of their habitat and threaten the well-being of other wildlife species, and in some instances, that of human health and safety [2]. Sunglasses vary greatly and many offer more style than protection. Hunting can be an important tool for wildlife management. It is possible to have lenses that look very dark and yet offer little ultraviolet protection. Some animals once considered varmints are now protected, such as wolves. Due to changes in the atmosphere, ultraviolet levels are much higher than in the past and ultraviolet protection for eyes and skin is even more important. Common varmints include various rodents, coyotes, crows, foxes, feral cats, and feral hogs.

Good sunglasses should also protect against ultraviolet light. Which species are "varmints" depends on the circumstance and area. plano) lenses that are darkened to provide protection against bright visible light. Some animals (such as wild rabbits or squirrels) may be utilized for fur or meat, but often no use is made of the carcass. Sunglasses may be made with either prescription or non-prescription (i.e. Varmint species are often responsible for detrimental effects on crops, livestock, landscaping, infrastructure, and pets. Main article: Sunglasses. While not an efficient form of pest control (poisoning and trapping are much more effective), it does provide recreation and is much less regulated.

Corrective glasses with plastic lenses can often be used in the place of safety glasses in many environments; this is one advantage that they have over contact lenses. Varmint hunting is an American phrase for the killing of non-game animals seen as pests. The pictured wraparound safety glasses are evidence of this style change with the close fitting nature of the wraparound dispensing with the need for side shields. The most common hunting weapons are bows, modern rifles or single-shot, muzzle-loading black powder rifles. Recent safety glasses have tended to be given a more stylish design, in order to encourage their use. Most hunters are encouraged to take a safety course and for additional safety some areas may be segregated by weapon type. They may provide less eye protection than goggles, face shields or other forms of eye protection, but their light weight increases the likelihood that they will actually be used. Technical specifications for hunting equipment and methods (such as the use of hounds) are strictly regulated, and hunters must purchase a special hunting license.

Some safety glasses are designed to fit over corrective glasses or sunglasses. In addition to addressing the legal status of animals, regulations govern the areas, seasons, techniques and methods hunters may use. The lenses of safety glasses can also be shaped for correction. Since birds do not recognize political borders, hunting of migratory waterfowl (ducks, geese, and others) is regulated by the United States Fish and Wildlife Service under treaties with Canada and Mexico. For example, those used in medicine may be expected to protect against blood splatter while safety glasses in a factory might have stronger lenses and a stronger frame with additional shields at the temples. Hunting of most mammals such as deer, elk and small game is regulated at the state level. Safety glasses can vary in the level of protection they provide. A key task of Federal and state park rangers and game wardens is to enforce laws and regulations related to hunting, included species protection, hunting seasons, and hunting bans.

Although safety lenses may be constructed from a variety of materials that vary in impact resistance, certain standards suggest that they maintain a minimum 1mm thickness at the thinest point regardless of material. States also collect monies from hunting licenses to assist with management of game animals, as designated by law. Safety glasses are usually made with shatter-resistant plastic lenses to protect the eye from flying debris. Proceeds from the Federal Duck Stamp, a required purchase for migratory waterfowl hunters, have purchased more than 5 million acres (20,000 km²) of habitat for the refuge system lands that support waterfowl and many other wildlife species, and are often open to hunting. Lenses made to conform to the prescription of an ophthalmologist or optometrist are called prescription lenses and are used to make prescription glasses. Each year, nearly $200 million in hunters' federal excise taxes are distributed to State agencies to support wildlife management programs, the purchase of lands open to hunters, and hunter education and safety classes. Glasses correcting for myopia will have negative diopter strengths. Two such private organizations are Ducks Unlimited and Delta Waterfowl.

Over-the-counter reading glasses are typically rated at +1.00 to +3.00 diopters. and state capitals [1]. The power of a lens is generally measured in diopters. Local hunting clubs and national organizations provide hunter education and help protect the future their sport by buying land to set aside as habitat or by lobbying in Washington, D.C. Corrective lenses modify the focal length of the eye to alleviate the effects of shortsightedness (myopia), longsightedness (hyperopia) or astigmatism. The Boone and Crockett Club is an excellent example of this: founded in 1887 to discourage commercial hunting, promote conservation and the "fair chase" ethic of hunting "individual animals in a manner that conserves, protects, and perpetuates the hunted population.". Either of these designs offers dramatically better ability to withstand the stresses of daily wear and the occasional accident. Current regulation of hunting within the United States goes back to the 1800's, and most modern hunters see themselves as conservationists and sportsmen, along the lines of Theodore Roosevelt.

Other frames have spring-loaded hinges. Hunting in the United States is not associated with any particular class or culture. For instance, it is now possible to purchase frames made of special memory metal alloys that return to their correct shape after being bent. It is common for rural Alaska Native communities to obtain 50-90% of their daily protein from hunting. Despite the increasing popularity of contact lenses and laser corrective eye surgery, glasses remain very common and their technology has not stood still. This is particularly true in Alaska, where people still feed on sea and land mammals as well as fish and birds. These designs were not immediately successful, however, and various styles with attached handles such as scissors glasses and lorgnettes remained fashionable throughout the 18th and into the early 19th century. In certain cases (such as the Marine Mammal Protection Act), Federal law provides explicit protection for Native American hunting rights.

The modern style of glasses, held by temples passing over the ears, was developed in 1727 by the British optician Edward Scarlett. North American hunting predates the United States by thousands of years and many Native American hunters retain key hunting rights through legal treaty as part of a long, cultural tradition. Girolamo Savonarola suggested that eyepieces could be held in place by a ribbon passed over the wearer's head, this in turn secured by the weight of a hat. The definition of game in the United Kingdom is governed by the Game Act 1831. Early eyepieces were designed to be either held in place by hand or by exerting pressure on the nose (pince-nez). The open season for grouse famously begins on August 12, the so-called Glorious Twelfth. Over time, the construction of spectacle frames also evolved. The shooting of game birds, especially pheasant and grouse, is a popular sport in the UK, with over a million participants per year.

The first lenses for correcting astigmatism were constructed by the British astronomer George Airy in 1827. Hunting deer by foot without hounds is called game stalking. The American scientist Benjamin Franklin, who suffered from both myopia and presbyopia, invented bifocals in 1784 to avoid having to regularly switch between two pairs of glasses. Other sorts of foxhounds may also be used for hunting stag, otter or weasel. However, it was not until 1604 that Johannes Kepler published in his treatise on optics and astronomy, the first correct explanation as to why convex and concave lenses could correct presbyopia and myopia. Sight hounds such as greyhounds may be used to run down hare in coursing with scent hounds such as beagles used for beagling, the hunting of hares on foot. Nicholas of Cusa is believed to have discovered the benefits of concave lens in the treatment of myopia (nearsightedness). Similar to fox hunting in many ways is the chasing of hare with hounds.

These early spectacles had convex lenses that could correct the farsightedness (presbyopia) that commonly develops as a symptom of aging. Some animal rights supporters feel that the suffering caused to foxes, horses and hounds are cruel and unnecessary, whilst proponents argue that it is a rural tradition, culturally and economically important. Bacon's published writings describe the magnifying glass (which he did not invent), but make no mention of glasses. The special rituals of the fox hunt and the controversy surrounding it are addressed in the articles fox hunting and fox hunting legislation. Other stories, possibly legendary, credit Roger Bacon with the invention. Originally a form of vermin control to protect livestock, it became a popular social activity for the upper classes in Victorian times, and a traditional rural activity for riders and foot followers alike. In 1738, a Florentine historian named Domenico Manni reported that a tombstone in Florence credited one Salvino d'Armato (died 1317) with the invention of glasses. The most controversial form of hunting in the United Kingdom is fox hunting.

Based on this evidence, Redi credited another Dominican monk, Fra Alessandro da Spina of Pisa, with the re-invention of glasses after their original inventor kept them a secret, a claim contained in da Spina's obituary record. The synonym Bloodless hunt for hunting with the use of film and a still photo camera was first used by the Polish photographer Włodzimierz Puchalski. In 1676, Franciscus Redi, a professor of medicine at the University of Pisa, wrote that he possessed a 1289 manuscript whose author complains that he would be unable to read or write were it not for the recent invention of glasses, and a record of a sermon given in 1305, in which the speaker, a Dominican monk named Fra Giordano da Rivalto, remarked that glasses had been invented less than twenty years previously, and that he had met the inventor. On the rise, even before integral ecotourism was, is the animal-friendly version known as photo-safari, where the only shots aimed at wildlife come from camera lenses. The identity of the original inventor is unknown, although a possible source is the Arabs, who may have had magnifying lenses in the 10th century. Among trophy hunters, those who outfitted the safaris themselves would receive the greatest admiration. Glasses were possibly invented in northern Italy, most likely in the late 1280s. A special safari type is the solo-safari where all the license acquiring, stalking, preparation and outfitting is done by the hunter himself.

. Hunters are usually tourists, accompanied by professional local guide, skinners and porters in more difficult terrains. Sunglasses protect against high levels of visible and ultraviolet light. Nowadays, it's often used to describe tours through African national parks to watch or hunt wildlife. Safety glasses are a kind of eye protection against flying debris or visible and near visible light or radiation. It is a several days or even weeks-lasting journey and camping in the bush or jungle, while pursuing big game. Corrective spectacles have lenses shaped to correct vision abnormalities, such as myopia. Safari as a distinctive way of hunting was popularized by US author Ernest Hemingway and president Theodore Roosevelt.

Hydrophobic coatings designed to ease cleaning are also available, as are anti-reflective coatings intended to improve night vision and make the wearer's eyes more visible. A safari (from Swahili word meaning a long journey) is an overland journey (especially in Africa). Scratch-resistant coatings can be applied to most plastic lenses giving them similar scratch resistance to glass. Other, independent republics (and neighbouring Himalayan monarchies, as Nepal) acted to curb such massively disturbing 'expeditions', in the name of conservation, although the threat of poaching, extirpation, and extinction reamin for many species and habitats. Some plastics have a greater index of refraction than most types of glass, allowing thinner lenses for a given prescription. After European guests of these princes had enjoyed the honour of talking part in these elephant hunts, some colonial Sahibs started organizing their own, and tiger numbers especially dwindled alarmingly. Some plastics also have more advantageous optical properties than glass, such as better transmission of visible light and greater absorption of ultraviolet light. As hunting was an important princely pass-time, worthy hunting lodges were constructed (not unlike feudal Europe).

Glasses were originally made from glass, but many are now made from plastic (often polycarbonate or CR-39) due to the danger of breakage and the greater weight of glass lenses. Bhils in Rajasthan's premier kingdom Mewar), because of their traditional knowledge of environment, techniques etc., but thus could be closer than most subjects to the ruler, who would often hunt big game (preferably the emperor of Asians wildlife, the (Bengal) tiger) in majestic style: on the back of an elephant, often commandeering extra helpers as drivers to scare the game out of the grass or jungle till it came within gun reach. In hipster slang they are cheaters. Often these were recruited from the normally low-ranking local pre-Aryan tribes (e.g. Spectacles is often shortened to specs. Since these had to be armed (not unlike he common lancer units; both could be mounted), they might also double as a supplementary police corps or military contingent. Glasses are more often called eyeglasses in North American English, occasionally spectacles in British English, and (rarely) frames or lenses. native professional hunters.

Historical types include the pince nez, monocle, and lorgnette. maintained a whole corps, attached to their court, of shikaris, i.e. Modern glasses are typically supported by pads on the bridge of the nose and by temples placed over the ears. During feudal and colonial epoch on the Indian continent, hunting was a true 'kingly sport' in the numerous princely states, as many (maha)rajas etc. Special glasses are used for viewing three-dimensional images or experiencing virtual reality. Although skilled recreational hunters may choose to become more selective hunters in attempts at taking a good representative animal, many people hunt not only to kill but to enjoy the outdoors in a way so few ever experience. Glasses, spectacles, or eyeglasses are frames bearing lenses worn in front of the human eyes, sometimes for purely aesthetic reasons but normally for vision correction or eye protection. Generally this also took two separate paths, recreational and trophy hunting.

Eyeglasses were a common part of the hipster persona, for example Dizzy Gillespie. In time, this aristocratic type of hunting lost its roots as a source of food and supplies, while retaining its prestigious nature as a sport, eagerly adopted by the rising middle class or bourgeoisie. Cheaters is used in the hipster argot. The importance of this proprietary view of game can be seen in the Robin Hood legends, in which one of the primary charges against the outlaws is that they "hunt the King's deer". Lenses is also sometimes used to refer to framed eyepieces, although it is not common. Game in these areas was certainly used as a source of food and furs, often provided via professional huntsmen; but it was also expected to provide a form of recreation for the aristocracy. Frames is sometimes used to refer to framed eyepieces, although it is not common. In most parts of medieval Europe, the upper-class (aristocracy and higher clergy) obtained as proud privilege the sole rights to hunt (and sometimes fish) in certain areas of a feudal territory.

In contrast, glass eye refers to a cosmetic prosthetic artificial eye that replaces a missing eye. Dangerous hunting, as for lions or wild boars, usually on horseback (or from a chariot, as in Pharaonic Egypt and Mesopotamia) also had function similar to tournaments and manly sports: an honourable, somewhat competetive pastime to help the aristocracy practice skills of war in times of peace. Eye glasses or eyeglasses is a word used in North American English. As game became more of a luxury than a necessity, the stylized pursuit of it also became a luxury. Also in frequent use is the shortened form, specs. Here in middle English the word "game" finds its meaning extended from a sport to an animal which is hunted. Spectacles is widely used in Britain and occasionally in the US, in addition to use by professional opticians. The other was the emergence of hunting as a sport for those of a higher social class.

Compare with other meanings of the word glass. One was that of the specialist hunter: rather than a general masculine task, hunting became one of many trades pursued by those with special training and equipment. Pair of glasses (or just glasses) is commonly used in Britain and in North America. As hunting moved from a subsistence activity to a social one, two trends emerged. Hunting may be used to kill animals who prey upon domestic animals or to extirpate native animals seen as competition for resources such as water or forage. Even as agriculture and animal husbandry become more prevalent, hunting often remains a part of human cultures where the environment and social conditions allow.

These are all associated with medieval hunting; in time various dog breeds were selected for very precise tasks during the hunt, reflected in such names as pointer and setter. With domestication of the dog, birds of prey and the ferret, various forms of animal-aided hunting developed including venery (scent hound hunting, such as fox hunting), coursing (sight hound hunting), falconry and ferreting. From the skins of sea mammals they may make water-proof kayaks, clothing, gloves and footwear. Inuit peoples in the Arctic trap and hunt animals for clothing, and produce complicated parkas consisting of up to 60 stitched pieces capable of with-standing sub-zero temperatures.

Hunting is still vital in marginal climates, especially those unsuited for pastoral uses or agriculture. Euripides' tale of Artemis and Acteon, for example, may be seen as a caution against disrespect of prey or impudent boasting. Taboos are often related to hunting, and mythological association of prey species with a divinity could be reflected in hunting restrictions such as a 'reserve' surrounding a temple . The cultural and psychological importance of hunting in ancient societies is represented by deities such as the horned god Cernunnos, or lunar goddesses of classical antiquity, Greek Artemis or Roman Diana.

The earliest hunting weapons would have included rocks, spears, the atlatl, bow and arrows. The supplementary meat and materials from hunting included protein (literally "the most important") food, bone for implements, sinew for cordage, fur and feathers for ornament, with rawhide and leather also used in clothing and shelter. Even as animal domestication became relatively widespread, hunting was usually a significant contributor to the human food supply, even after the development of agriculture. Before the widespread domestication of animals, hunting was a crucial component of hunter-gatherer societies, and is a theme of many stories and myths, as well as many proverbs, aphorisms, adages and metaphors even today.

. Neither is it considered hunting to pursue animals without intent to possibly kill, as in wildlife photography or birdwatching, or to "hunt" for plants (such as mushrooms). Trapping is also usually considered a separate activity. The pursuit, capture and killing of fish is called fishing, which is not commonly categorized as a kind of hunting, although many hunters may also fish.

Wildlife managers are frequently part of hunting regulatory and licensing bodies, where they help to set rules on the number, manner and conditions in which game may be hunted or "harvested.". Hunting may be a component of modern wildlife management, but is only a portion, sometimes used to help maintain a population of healthy animals within an environment's ecological carrying capacity. By definition, hunting excludes the killing of individual animals that have become dangerous to humans and the killing of non-game animals, domestic animals, or vermin (or "varmints") as a means of pest control. The killing of other humans is most often called homicide, genocide or war.

Hunted animals are referred to (and often protected by law) as game animals, and are usually large mammals or migratory birds. In modern use, the term refers to regulated and legal hunting, as distinguished from poaching, which is the killing, trapping or capture of animals contrary to law. Hunting is the practice of humans pursuing animals to capture or kill them for food, sport, or trade in their products. Trapping is the use of devices (snares, pits, deadfalls) to capture or kill an animal.

Tracking is the practice of reading physical evidence in pursuing animals. Still Hunting is the practice of walking quietly in search of animals. Stalking is the practice of walking quietly, often in pursuit of an identified animal. Spotlighting is the use of artificial light to find or blind animals before killing.

Scouting includes a variety of tasks and techniques for finding animals to hunt. Glassing is the use of optics (such as binoculars) to more easily locate animals. Flushing is the practice of scaring animals from concealed areas. Driving is the herding of animals in a particular direction, usually toward another hunter in the group.

Dogs may be used to help flush, herd, drive, track, point at, pursue or retrieve prey. Camouflage is the use of visual concealment (or scent) to blend with the environment. Calling is the use of animal noises to attract or drive animals. Blind or Stand hunting is waiting for animals from a concealed or elevated position.

Baiting is the use of decoys, lures, scent or food to attract animals.

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