Variations
Glasses can be very simple, such as magnifying lenses which are used to treat mild hyperopia and presbyopia can be bought off the shelf, normally referred to as reading glasses. Most glasses are made to a particular prescription, based on degree of myopia or hyperopia combined with astigmatism. Lenses can be ground to specific prescriptions, but in some 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. Some modern multifocal lenses, such as Progressive lenses (known as "no-line bifocals"), give a smooth transition between these different focal points and is unnoticeable by most wearers, while others have lenses specifically intended for use with computer monitors at a fixed distance. People may have several pairs of glasses, one for each task or distance, with specific glasses for reading, computer use, television watching, and writing.
Rimless
Three-piece rimless and semi-rimless glasses are common variations that differ from regular glasses in that their frames do not completely encircle the lenses. Three-piece rimless glasses have no frame around the lenses, and the bridge and temples are mounted directly onto the lenses. Semi-rimless (or half-rimless) glasses have a frame that only partially encircles the lenses (commonly the top portion), which are held in place most often by high strength nylon wire.[13] A rare and currently non commercial variation are rimless and frameless glasses attached to a piercing at the bridge of a wearers nose.[14] Such glasses have the visual look of the pince-nez.
Glazing
Spectacle lenses are edged into the frame's rim using glazing machines operated by ophthalmic technicians. The edging process begins with a trace being taken of the frame's eye shape. In earlier days the trace was replicated onto a plastic pattern called a Former. Nowadays the process is patternless and the shape is sent to the edger electronically.
The lens, in the form of a round uncut, is positioned in the correct manner to match the prescription and a block is stuck to the lens and that block fits into a chuck in the edging machine. A diamond coated wheel spins as the edger replicates the frame's eye-shape to the uncut lens. A 'v' bevel is applied to allow the edge of the lens to fit into the frame rim.
Fashion
United States senator Barry Goldwater in Horn-rimmed glasses.Glasses can be a major part of personal expression, from the extravagance of Elton John and Dame Edna Everage, from Groucho Marx to Buddy Holly.
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; they are actually 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. John Lennon wore his round-lens 'Windsor' spectacles from some of his time with the Beatles to his murder in 1980. Rock band Weezer are known for some of the members wearing thick-rimmed glasses.
Glasses can be used jokingly as a stereotype for intelligence.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. Some people who find that wearing glasses may look nerdy turn to contact lenses instead, especially under peer pressure. Others turn to laser eye surgery, as do some would-be pilots.
Another unpopular aspect of glasses is their inconvenience. Even through 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 can become greasy or trap vapour when eating hot food, swimming, walking in rain or rapid temperature changes (such as walking into a warm building from cold temperatures outside), 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.
