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Spectacles
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Spectacles

   

Spectacles, eyeglasses, or glasses are frames bearing lenses worn in front of the eyes, sometimes for purely aesthetic reasons but normally for vision correction or eye protection. Special glasses are used for viewing 3-D film images or stereoscopic virtual reality.

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

Spectacles are more often called eyeglasses in North American English, glasses in North American and British English, and (rarely) frames or lenses. "Spectacles" is often shortened to specs. Also see usage of words for eyepieces for a more detailed examination of the different usages for these words.

Spectacles were originally made from glass, but many are now made from plastic due to the danger of breakage and the greater weight and thickness of glass lenses. Glass lenses, on the other hand, are much less susceptible to scratching.

Corrective spectacles have lenses shaped to correct some kinds of vision abnormalities.

Safety spectacles are a kind of eye protection that protects against flying debris but may also protect against visible and near visible light or radiation.

Sun spectacles protect against high levels of visible and ultraviolet light.

Table of contents
1 Corrective spectacles
2 Safety spectacles
3 Sunglasses
4 Special spectacles
5 Conditions spectacles are used to correct
6 Spectacles as a fashion accessory
7 Other types of glasses
8 See also
9 External links

Corrective spectacles

Corrective lenses modify the focal length of the eye's pupil to alleviate the effects of shortsightedness (myopia), longsightedness (hyperopia) or astigmatism. In North America lenses made to conform to the prescription of an ophthalmologist or optometrist are called prescription lenses and are used to make prescription glasses.

Safety spectacles

Safety spectacles are usually made with shatter-resistant plastic lenses to protect the eye from flying debris. Safety spectacles can vary in the level of protection they provide. For example, those used in medicine may be expected to protect only 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 spectacles can also be shaped for correction or tinted to protect against visible and near-visible radiation. Some safety spectacles are designed to fit over corrective spectacles or sunglasses. Safety spectacles 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. Recently, safety spectacles have been given a more stylish design to increase their use.

Corrective spectacles with plastic lenses can often be used as safety spectacles in many environments; this is one advantage that they have over contact lenses.

Sunglasses

Sunglasses are darkened spectacles that provide protection against bright visible and ultraviolet light. Due to changes in the atmosphere, ultraviolet levels are higher than in the past and ultraviolet protection for eyes and skin is even more important. Sunglasses vary greatly and many offer more style than protection. It is possible to have lenses that look very dark and yet offer little ultraviolet protection.

Prescription lenses may be used to make prescription sunglasses.

Special spectacles

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

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

Conditions spectacles are used to correct

Spectacles fitted with corrective lenses are a common means of correcting focus problems such as myopia (nearsightedness, short-sightedness) and hypermetropia (farsightedness, long-sightedness). Myopic people cannot focus at long distances; people with hypermetropia cannot focus at close distances. Astigmatism is mismatched focusing horizontally and vertically. As people age they develop presbyopia, which limits their ability to focus on nearby objects. None of these conditions is considered a disease.

Spectacles 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 spectacles 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 come to need 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, an early eyeglass-wearing celebrity.

Some modern multifocal lenses give a smooth transition between these lenses, unnoticeable by most wearers. Other spectacle wearers sometimes have lenses specifically intended for use with computer monitors at a fixed distance. On the other hand, many people simply have several pairs of spectacles, one for each task or distance.

Spectacles as a fashion accessory

Spectacles 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 spectacles, and spectacles are available in a wide range of styles, materials, and even designer labels.

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

For some celebrities, spectacles form part of the identity. American Sen. Barry Goldwater continued to wear lensless horn-rimmed spectacles after being fitted with contact lenses because he was not recognizable without his trademark spectacles. 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 spectacles that contain no lenses, but are in fact a bone-conducting hearing aid.

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

Halo effect refers to the stereotype that the wearers of spectacles are intelligent or, especially in teen culture, even geeks. This is a conception rooted in that the first people to wear spectacles were those who did a lot of reading in an era when most people were illiterate. Some of those who find that wearing glasses may look nerdy, so turn to contact lenses instead. Some celebrities have mildly been accused of vanity because of this.

Another unpopular aspect with spectacles are their inconvenience. Even after mid-20th century, when light frames, such as of titanium, and very flexible ones were created, glasses still can cause problems during rigorous sports. The glass itself also can become greasy or trap vapour when eating hot food or swimming or walking in rain, reducing visibility significantly. Scraping, fracturing, and worse, breakage of the glass require time-consuming and costly professional repair.

Other types of glasses

Other kinds of spectacles include tinted protective lenses, ranging from sunglasses, which protect the eye from glare and ultraviolet radiation, to specialized units that protect against extreme brightness and are used for welding and viewing eclipses.

Prescription sunglasses (term used by most laymen) or sun-spectacles (the term used by some optometrists), which combine protection from bright light with vision correction, have become fairly common. Some spectacles have photo-sensitive lenses that darken as the light grows brighter. They are sunglasses and indoor spectacles in one.

There are also safety spectacles that are made of rigid plastic and designed to protect the eyes from flying objects. Some of these may have a prescription as well.

Spectacles fitted with differently coloured or polarized lenses can be used to view three-dimensional images.

See also

External links