Glasses

Glasses, also known as eyeglasses or spectacles, are devices consisting of lenses mounted in a frame that holds them in front of a person's eyes. Glasses are typically used for vision correction. Safety glasses provide eye protection against flying debris or against visible and near-visible light or radiation. Sunglasses allow better vision in bright daylight, and may protect one's eyes against damage from high levels of ultraviolet light. Specialized glasses may be used for viewing specific visual information (such as stereoscopy). Sometimes glasses are worn simply for aesthetic or fashion purposes. The number of Americans who are nearsighted has doubled since the 1970s and almost 3/4 of the US population wears glasses. People are more likely to need glasses the older they get with 93% of people between the age of 65-75 wearing corrective lenses.

History

Precursors

The use of a convex lens to form an enlarged/magnified image is discussed in Alhazen's Book of Optics (1021). Its translation into Latin from Arabic in the 12th century was instrumental to the invention of eyeglasses in 13th century Italy.