Bifocals
DETAILS:
Prior to the invention of bifocal eyeglasses, people suffering from both near (myopic) and far (presbyopic) sight would have to switch back and forth between two pairs of glasses depending on what they were trying to see. Then in 1784, Benjamin Franklin* created a way to incorporate the two eyeglasses into one.
Known as “Franklin” bifocals, two lenses were simply cut in half, placed one above the other, and then held in place via the eyeglass frame. Though the design was crude and the split lines distracting, Franklin’s innovation helped popularize the use of bifocal lenses.
Bifocals today have the two different corrective lenses molded into one, with the near-sighted lens on the lower half while the far-sighted lens is on top.
Today there are now trifocals for people who suffer from intermediate vision problems, as well as progressive lenses that help people who suffer from a variety of different visual ailments.
ONELINER: Bifocals
EXTRA-CONNECTIONS: None
BIBLIOGRAPHY:
Encyclopedia Britannica
http://en.wikipedia.org/wiki/Bifocals