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bifocal glasses 1

Ben had poor vision and needed glasses to read. He got tired of constantly taking them off and putting them back on, so he decided to figure out a way to make his glasses let him see both near and far. He had two pairs of spectacles cut in half and put half of each lens in a single frame. Today, we call them bifocals.

 

Glass lenses, for use as magnifiers or for starting fires, date to about 300 BC, but the first eyeglasses to aid or correct vision were almost certainly invented in 1280 in Florence, Italy by the Dominican friar Alessandro della Spina and / or his friend, the physicist Salvino degli Armati.   Prescribed for far-sightedness, the glasses had convex lenses and were worn by Armati, who had injured his eyes while performing light refraction experiments and discovered that it was possible to enlarge the appearance of objects by looking through two pieces of convex glass.
It was in the early fourteenth century that concave lenses were used to correct near-sightedness.  In fact, Pope Leo X  was depicted wearing glasses, with concave lenses, in a 1517 painting by Raphael.  Whereas early eyeglasses were made of polished quartz, by the sixteenth century developments in glassmaking made it possible to mass produce them from glass.

Bifocals, the combination of both concave and convex lenses for both types of vision correction, a top lens for distant viewing and a lower lens for reading, were developed around 1760 by the American statesman and inventor Benjamin Franklin.

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