Eyeglasses: Their Background And Variety

Corrective laser surgery and contact lenses have increasingly helped people adjust

their vision problems, but eyeglasses remain a popular tool for seeing what we need to perceive. Often referred to as "glasses," or "spectacles" in the past, eyeglasses set a plastic or glass lens in front of each eye with a frame perched on the nose and wings that rest on the ears. Those are called temple arms.

The first known reference to magnification appears in Egyptian hieroglyphs from the 5th century BCE. Seneca the Younger, born a few years before Jesus, was the first to write about artificial magnification. But eyeglasses as we recognize them did not turn up until the 13th or 14th century, in Italy. As many of us learned in school, bifocals were invented by a scientist named Benjamin Franklin, who needed a tool to correct his nearsightedness.

Since Franklin's time, reading glasses have evolved into an array of alternatives. Half-glasses in the Franklin style sit low on the nose. Split lens bifocals, with a clear line between an upper half for distant vision and a lower half for reading close up, have given way to lenses that smoothly change from one to the other, and even three or more different resolutions in a single lens.

Millions of plain, non-prescription reading glasses sell off the shelves of pharmacies and department store chains in the United States. Customers seeking to sharpen their vision bought roughly 30 million units of reading glasses each year in the 1990s.

The disadvantages of eyeglasses include damage and smudging. Glass or plastic lenses can break or become scratched over time, which entails costly repairs or replacement. Dirt, food grease, and body oils can cloud them, and sudden changes in ambient temperature or rainfall also fog and blur eyeglasses temporarily.

Sunglasses continue to be a popular form of eyeglass wear. Darkened lenses protect the wearer's eyes from bright sunshine and fluorescent lights, and ultraviolet radiation if designed for that. Gray or gray-green shading is the best for keeping colors natural. Elderly persons or people with impaired sight like yellow-tone sunglasses because they heighten color contrast and render better depth perception. Brown lenses are favored by golfers, but they do not preserve natural colors as accurately. Sunglasses also come in blue, purple, dark green, and other tones for appearance.

Safety glasses, typically larger and designed to fit snugly against the skin around the eyes (and even other eyeglasses), protect against anything from blood or wood chip splatter to flying metal and electric sparks for welders. They are typically constructed of polycarbonates, a light but shatter-resistant type of plastic.

Musicians such as John Lennon and Buddy Holly made eyeglasses, long regarded as unfashionable, more attractive to young people. Longtime eyeglass and sunglass makers like Polaroid, Ray Ban, and Vuarnet were joined by high fashion names including Versace, Laura Ashley, and Tommy Hilfiger. In the late twentieth century, celebrities -- among them Diahann Carroll, Dale Earnhart Jr., Joan Collins, and even Scooby Doo -- granted permission for their names to appear as brands of eyeglasses.

by: clairebeicker

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