Glasses, also known as eyeglasses, spectacles, or colloquially as specs, are vision eyewear with clear or tinted lenses mounted in a frame that holds them in front of a person's Human eyes, typically utilizing a bridge over the nose and hinged arms, known as temples or temple pieces, that rest over the ears for support.
Glasses are typically used for Corrective lens, such as with reading glasses and glasses used for nearsightedness; however, without the specialized lenses, they are sometimes used for cosmetic purposes.
Safety glasses are eye protection, a form of personal protective equipment (PPE) that are worn by workers around their eyes for protection. Safety glasses act as a shield to protect the eyes from any type of foreign debris that may cause irritation or injury; these glasses may have protection on the sides of the eyes as well as in the lenses. Some types of safety glasses are used to protect against visible and near-visible light or radiation. Glasses are worn for eye protection in some sports, such as squash.
Glasses wearers may use a strap to prevent the glasses from falling off. Wearers of glasses that are used only part of the time may have the glasses attached to a cord that goes around their neck to prevent the loss and breaking of the glasses.
Sunglasses allow for better vision in bright daylight and are used to protect one's eyes against damage from excessive levels of ultraviolet light. Typical sunglasses lenses are tinted for protection against bright light or polarized to remove glare; photochromic glasses are clear or lightly tinted in dark or indoor conditions, but turn into sunglasses when they come into contact with ultraviolet light. Most over-the-counter sunglasses do not have corrective power in the lenses; however, special prescription sunglasses can be made. People with conditions that have photophobia as a primary symptom (like certain migraine disorders) often wear sunglasses or precision tinted glasses, even indoors and at night.
Specialized glasses may be used for viewing specific visual information, for example, 3D glasses for 3D films (stereoscopy). Sometimes glasses are worn purely for fashion or aesthetic purposes. Even with glasses used for vision correction, a wide range of fashions are available, using plastic, metal, wire, and other materials for frames. Most glasses lenses are made of plastic, polyethylene, and glass.
Corrective lenses bring the image back into focus on the retina. They are made to conform to the prescription of an ophthalmologist or optometrist. A lensmeter can be used to verify the specifications of an existing pair of glasses. Corrective eyeglasses can significantly improve the life quality of the wearer. Not only do they enhance the wearer's visual experience, but can also reduce problems that result from eye strain, such as headaches or squinting.
The most common type of corrective lens is "single vision", which has a uniform refractive index. For people with presbyopia and hyperopia, bifocals and trifocal glasses provide two or three different refractive indices, respectively, and progressive lenses have a continuous gradient. Lenses can also be manufactured with high refractive indices, which allow them to be more lightweight and thinner than their counterparts with "low" refractive indices.
Reading glasses provide a separate set of glasses for focusing on close by objects. Reading glasses are available without prescription from , and offer a cheap, practical solution, though these have a pair of simple lenses of equal power, and so will not correct refraction problems like astigmatism or refractive or prismatic variations between the left and right eye. For the total correction of the individual's sight, glasses complying to a recent ophthalmic prescription are required.
People who need glasses to see often have corrective lens restrictions on their driver's licenses that require them to wear their glasses every time they drive or risk fines or jail time.
Some militaries issue prescription glasses to servicemen and women. These are typically GI glasses. Many state prisons in the United States issue glasses to inmates, often in the form of clear plastic aviators.
Adjustable-focus eyeglasses might be used to replace bifocals or trifocals, or might be used to produce cheaper single-vision glasses (since they do not have to be custom-manufactured for every person). Pinhole glasses are a type of corrective glasses that do not use a lens. Pinhole glasses do not actually refract the light or change focal length. Instead, they create a diffraction limited system, which has an increased depth of field, similar to using a small aperture in photography. This form of correction has many limitations that prevent it from gaining popularity in everyday use. Pinhole glasses can be made in a DIY fashion by making small holes in a piece of card which is then held in front of the eyes with a strap or cardboard arms.
Glasses may also house other corrective or assistive devices. After the development of the transistor in the 1940s, combined eyeglass-hearing aids became popular. With thick-rimmed glasses the fashion at the time, a hearing aid could be concealed in the temple part of the frame. These fell out of fashion after the 1970s, but there are still occasions when combined eyeglass-hearing aids may be useful.
Light polarization is an added feature that can be applied to sunglass lenses. Polarization filters are positioned to remove horizontally polarized rays of light, which eliminates glare from horizontal surfaces (allowing wearers to see into water when reflected light would otherwise overwhelm the scene). Polarized sunglasses may present some difficulties for pilots since reflections from water and other structures often used to gauge altitude may be removed. Liquid-crystal displays emit polarized light, making them sometimes difficult to view with polarized sunglasses. Sunglasses may be worn for aesthetic purposes, or simply to hide the eyes. Examples of sunglasses that were popular for these reasons include tea shades and mirrorshades. Many blindness people wear nearly opaque glasses to hide their eyes for cosmetic reasons. Many people with light sensitivity conditions wear sunglasses or other tinted glasses to make the light more tolerable.
Sunglasses may also have corrective lenses, which requires a prescription. Clip-on sunglasses or sunglass clips can be attached to another pair of glasses. Some wrap-around sunglasses are large enough to be worn over another pair of glasses. Otherwise, many people opt to wear to correct their vision so that standard sunglasses can be used.
Anaglyph 3D glasses have a different colored filter for each eye, typically red and blue or red and green. A polarized 3D system on the other hand uses polarized filters. Polarized 3D glasses allow for color 3D, while the red-blue lenses produce an image with distorted coloration. An active shutter 3D system uses electronic shutters. Head-mounted displays can filter the signal electronically and then transmit light directly into the viewer's eyes.
Anaglyph and polarized glasses are distributed to audiences at 3D movies. Polarized and active shutter glasses are used with many home theaters. Head-mounted displays are used by a single person, but the input signal can be shared between multiple units.
Long hours of computer use (not blue light) may cause eye strain. Many eye symptoms caused by computer use will lessen after the usage of the computer is stopped. Decreasing evening screen time and setting devices to night mode will improve sleep. Several studies have shown that blue light from computers does not lead to eye diseases, including macular degeneration. The total amount of light entering the eyes can be adjusted without glasses using the screen brightness settings. Similarly, the blue light can often specifically be adjusted using the "night mode" of different operating systems, which can usually be activated outside of nighttime hours.
The American Academy of Ophthalmology (AAO) does not recommend special eyewear for computer use, although it recommends using prescription glasses measured specifically for computer screen distance (depending on individuals, but possibly 20–26 inches from the face), which are not the same as "blue-light blocking" glasses. The position of the College of Optometrists (UK) is that "the best scientific evidence currently available does not support the use of blue-blocking spectacle lenses in the general population to improve visual performance, alleviate the symptoms of eye fatigue or visual discomfort, improve sleep quality or conserve macula health."
Bifocals, Trifocal lenses, and generally require a taller lens shape to leave room for the different segments while preserving an adequate field of view through each segment. Frames with rounded edges are the most efficient for correcting myopia prescriptions, with perfectly round frames being the most efficient. Before the advent of eyeglasses as a fashion item, when frames were constructed with only functionality in mind, virtually all eyeglasses were either Windsor glasses, oval, panto, rectangular, octagonal, or square. It was not until glasses began to be seen as an accessory that different shapes were introduced to be more aesthetically pleasing than functional.
The use of a convex lens to form an enlarged/magnified image was most likely described in Ptolemy's Optics (which survives only in a poor Arabic translation). Ptolemy's description of lenses was commented upon and improved by Ibn Sahl (10th century) and most notably by Ibn al-Haytham ( Book of Optics, ). Latin translations of Ptolemy's Optics and of Alhazen became available in Europe in the 12th century, coinciding with the development of "".
There are claims that single lens magnifying glasses were being used in China during the Northern Song dynasty (960–1127).
Robert Grosseteste's treatise De iride ( On the Rainbow), written between 1220 and 1235, mentions using optics to "read the smallest letters at incredible distances". From Grant's English translation of Robert Grosseteste's De Iride (On the rainbow) in Latin, p. 389: "This part viz, of perspective, if perfectly understood, shows us how to make nearby objects appear very small, and how to make a small object placed at a distance appear as large as we wish, so that it would be possible to read minute letters from incredible distances or count sand, seeds, blades of grass, or any minute objects." A few years later in 1262, Roger Bacon is also known to have written on the magnifying properties of lenses.Bacon, Roger; Burke, Robert Belle, trans. (1962) The Opus Majus of Roger Bacon (New York: Russell & Russell, Inc.) vol. 2. Part 5, Ch. IV, p. 582. From p. 582: "For we can so shape transparent bodies, and arrange them in such a way with respect to our sight and objects of vision, that the rays will be refracted and bent in any direction we desire, and under any angle, we wish we shall see the object near or at a distance. Thus from an incredible distance we might read the smallest letters and number grains of dust and sand ..." The development of the first eyeglasses took place in northern Italy in the second half of the 13th century.
Independently of the development of optical lenses, some cultures developed "sunglasses" for eye protection, without any corrective properties. For example, flat panes of smoky quartz were used in 12th-century China, and the Inuit have used snow goggles for eye protection.
The first eyeglasses were estimated to have been made in Central Italy, most likely in Pisa or Florence, by about 1290: In a sermon delivered on 23 February 1306, the Dominican Order friar Giordano da Pisa (–1311) wrote "It is not yet twenty years since there was found the art of making eyeglasses, which make for good vision ... And it is so short a time that this new art, never before extant, was discovered. ... I saw the one who first discovered and practiced it, and I talked to him."
Giordano's colleague Friar Alessandro della Spina of Pisa (d. 1313) was soon making eyeglasses. The Ancient Chronicle of the Dominican Monastery of St. Catherine in Pisa records: "Eyeglasses, having first been made by someone else, who was unwilling to share them, he Spina made them and shared them with everyone with a cheerful and willing heart." Venice quickly became an important center of manufacture, especially due to using the high-quality glass made at Murano. By 1301, there were guild regulations in Venice governing the sale of eyeglasses and a separate guild of Venetian spectacle makers was formed in 1320. In the fourteenth century, they were very common objects: Francesco Petrarca says in one of his letters that, until he was 60, he did not need glasses,Petrarch (Franciscus Petrarca) mentions eyeglasses in his Epistola ad Posteros (Letter to Posterity): English translation: and Franco Sacchetti mentions them often in his Trecentonovelle.
The earliest pictorial evidence for the use of eyeglasses is Tommaso da Modena's 1352 portrait of the cardinal Hugh de Saint-Cher reading in a scriptorium. Another early example would be a depiction of eyeglasses found north of the Alps in an altarpiece of the church of Bad Wildungen, Germany, in 1403. These early glasses had convex lenses that could correct both hyperopia (farsightedness), and the presbyopia that commonly develops as a symptom of aging. Although concave lenses for myopia (near-sightedness) had made their first appearance in the mid-15th century, it was not until 1604 that Johannes Kepler published the first correct explanation as to why convex and concave lenses could correct presbyopia and myopia.
Early frames for glasses consisted of two magnifying glasses together by the handles so that they could grip the nose. These are referred to as "rivet spectacles". The earliest surviving examples were found under the floorboards at Kloster Wienhausen, a convent near Celle in Germany; they have been dated to circa 1400.
The world's first specialist shop for spectacles—what we might regard today as an optician—opened in Strasbourg (then Holy Roman Empire, now France) in 1466.
Marco Polo is mistakenly claimed to have encountered eyeglasses during his travels in China in the 13th century. However, no such evidence appears in his accounts. Section Geschichte der Brillen (History of Eyeglasses) From pp. 266–267 (translated): "3. Do the Europeans have the Chinese to thank for eyeglasses? ... Messrs. Scrini and Fortin in Paris have asserted this recently with the words: 'One knows, on the other hand, that when Marco Polo went to China, he learned that for a very long time already, the inhabitants had been using eyeglasses.' This assertion lacked any substantiation. So I have closely perused the German translation of 'the books of Marco Polo' (2nd ed., Leipzig 1855) once again as well as carefully compared that to the original text (the book of Marco Polo by Pauthier, Paris 1865, 2 volumes): not a syllable about eyeglasses in China is found therein. Our highly esteemed Sinologist, Prof. Graube, had the kindness to peruse also the English edition (by Yule, London 1875), with the same negative result. Thus the sentence of Messrs. Scrini and Fortin is to be crossed out; this error may not be the only one to have infiltrated the literature." Indeed, the earliest mentions of eyeglasses in China occur in the 15th century and those Chinese sources state that eyeglasses were imported.
In 1907, Professor Berthold Laufer speculated, in his history of glasses, that for glasses to be mentioned in the literature of China and Europe at approximately the same time it was probable that they were not invented independently, and after ruling out the Turks, proposed India as a location.Laufer, Berthold (1907). "Geschichte der Brille" History. Mitteilungen zur Geschichte der Medizin und der Naturwissenschaften Communications, 6 (4) : 379–385. However, Joseph Needham stated that the mention of glasses in the Chinese manuscript Laufer used "in part" to credit the prior invention of them in Asia did not exist in older versions of that manuscript, and the reference to them in later versions was added during the Ming dynasty.
In 1971, Rishi Agarwal, in an article in the British Journal of Ophthalmology, states that Vyasatirtha was observed in possession of a pair of glasses in the 1520s, he argues that it "is, therefore, most likely that the use of lenses reached Europe via the Arabs, as did Hindu mathematics and the ophthalmological works of the ancient Hindu surgeon Sushruta", but all dates are given well after the existence of eyeglasses in Italy was established, including significant shipments of eyeglasses from Italy to the Middle East, with one shipment as large as 24,000 glasses,Renaissance Vision from Spectacles to Telescopes, Vincent Ilardi, American Philosophical Society 2007 pages 118–125 as well as a spectacles dispensary in Strasbourg in 1466.
Over time, the construction of frames for glasses 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 sometime before 1727, possibly by the British optician Edward Scarlett. These designs were not immediately successful, however, and various styles with attached handles such as "scissors-glasses" and were also fashionable from the second half of the 18th century and into the early 19th century.
In the early 20th century, Moritz von Rohr and Zeiss (with the assistance of H. Boegehold and A. Sonnefeld) developed the Zeiss Punktal spherical point-focus lenses that dominated the eyeglass lens field for many years. In 2008, Joshua Silver designed eyewear with adjustable corrective glasses. They work by using a built-in syringe to pump a silicone solution into a flexible lens.
Despite the popularity of contact lenses and laser corrective eye surgery, glasses remain very common, as their technology has improved. 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 offer dramatically better ability to withstand the stresses of daily wear and the occasional accident. Modern frames are also often made from strong, lightweight materials such as titanium alloys, which were not available in earlier times.
Graham Pullin describes how devices for disability, like glasses, have traditionally been designed to camouflage against the skin and restore ability without being visible. In the past, design for disability has "been less about projecting a positive image as about trying not to project an image at all". Pullin uses the example of spectacles, traditionally categorized as a medical device for "patients", and outlines how they are now described as eyewear: a fashionable accessory. Much like other fashion designs and accessories, eyewear is created by designers, has reputable labels, and comes in collections, by season and designer. In recent years, it has become more common for consumers to purchase eyewear with non-prescription lenses as a fashion accessory.
There are claims that insufficiently free market competition inflates the prices of frames, which cost an average of $25–$50 U.S. to make, to an average retail price of $300 in the United States. This claim is disputed by some in the industry.
The United States also prohibits the sale of glasses unless the user has a recent prescription from an optometrist or ophthalmologist, whereas in most of the world, glasses and contact lenses can be bought without needing to get a new eye exam first. This means that Americans who lose or break their glasses may be unable to see well until they can get, and pay for, an appointment with an optometrist. In most of the world, someone who has lost their glasses merely goes to the nearest store selling glasses and buys a replacement over the counter.
In the United Kingdom, wearing glasses was characterized in the nineteenth century as "a sure sign of the weakling and the mollycoddle", according to Neville Cardus, writing in 1928. Ernest Killick was the first professional cricketer to play while wearing glasses "continuously", after his vision deteriorated in 1897. "With their aid he placed himself in the forefront among English professionals of all-round abilities." The American tenor Jan Peerce, plagued with poor eyesight, credited comedian Steve Allen for normalizing and even popularizing the wearing of eyeglasses in front of live television and stage audiences; prior to this, performers who read on early television were expected to squint or use contact lenses.
Since then, eyeglasses have become an acceptable fashion item and often act as a key component in individuals' personal image. Musicians Buddy Holly and John Lennon became synonymous with the styles of eye-glasses they wore to the point that thick, black horn-rimmed glasses are often called "Buddy Holly glasses" and perfectly round metal eyeglass frames called "John Lennon glasses" (or, more recently, "Harry Potter glasses"). British comedic actor Eric Sykes was known in the United Kingdom for wearing thick, square, horn-rimmed glasses, which were in fact a sophisticated hearing aid that alleviated his deafness by allowing him to "hear" vibrations. Some celebrities have become so associated with their eyeglasses that they continued to wear them even after taking other measures against vision problems: U.S. Senator Barry Goldwater and comedian Drew Carey continued to wear non-prescription glasses after being fitted for contacts and getting LASIK, respectively.
Other celebrities have used glasses to differentiate themselves from the characters they play, such as Anne Kirkbride, who wore oversized 1980s-style round horn-rimmed glasses as Deirdre Barlow in the soap opera Coronation Street; and Masaharu Morimoto, who wears glasses to separate his professional persona as a chef from his stage persona as Iron Chef Japanese. In 2012, some NBA players wore lensless glasses with thick plastic frames like horn-rimmed glasses during Post-game show, geek chic that draws comparisons to actor Jaleel White's infamous styling as TV character Steve Urkel.Archived at Ghostarchive and the Wayback Machine:
In superhero fiction, eyeglasses have become a standard component of various heroes' disguises as masks, allowing them to adopt a nondescript demeanor when they are not in their superhero personae: Superman is well known for wearing 1950s-style horn-rimmed glasses as Clark Kent, while Wonder Woman wears either round, Harold Lloyd-style glasses or 1970s-style bug-eye glasses as Diana Prince. An example of the halo effect is seen in the stereotype that those who wear glasses are intelligent. This belief can have positive consequences for people who wear glasses, for example in elections. Studies show that wearing glasses increases politicians' electoral success, at least in .
Later developments
In fashion
Widespread availability
Society and culture
Market
United States
Redistribution
Fashion
Personal image
Styles
See also
Explanatory notes
General and cited bibliography
External links
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