People have been using simple lenses for magnification for more than a thousand years. Eyeglasses have been in use since the 14th century. In Europe, eyeglasses first appeared in Italy and then spread to the various royal courts until eventually there were trained lens grinders in all European countries. By the 17th century, these craftsworkers had banded together into an association called a guild.
The first eyeglass lenses were convex (that is, they were thicker in the middle than at the edges). This is the shape used to correct farsightedness. There is no evidence of concave lenses (thicker at the edges than in the middle) for nearsightedness until the 16th century. Benjamin Franklin developed eyeglasses further by inventing the bifocal lens in the 18th century. In 1801, Thomas Young discovered the eye condition called astigmatism, in which rays from a perceived object fail to meet at one focal point, causing blurred and imperfect vision. Cylindrical and compound lenses were developed to correct astigmatisms approximately 25 years later.
Ophthalmic laboratory technicians often use computerized lens analyzers to measure the preciseness of newly ground contact lenses. In 1887, a Swiss physician, A. E. Fick, made the first contact lens. These first lenses were made of heavy glass, exerted an uncomfortable pressure on the eyeball, and were difficult to fit. In the late 1930s, a light plastic was developed that could be easily molded to the shape of the eye. In 1950, a lens that floated on the wearer's tears was introduced; and today, an even smaller lens, covering only the cornea, is in widespread use.
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