Why did Benjamin Franklin invent bifocals?

Benjamin Franklin invented bifocals largely because his eyesight was deteriorating, and he was tired of switching back and forth between different pairs of glasses.

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As well as being one of the Founding Fathers of the United States, Benjamin Franklin was also a man of science and an inventor. Many of his inventions are still with us today, most notably bifocals.

As with many inventions, bifocals came out of a pressing personal need. Franklin was getting on in life and, as is often the case with the aged, was starting to experience a notable deterioration in his eyesight.

Franklin, who was both short and long-sighted, used two pairs of spectacles, one for reading and the other for seeing at distances. As one can imagine, he found it incredibly tiresome and annoying to keep switching between two pairs of glasses.

So he came up with the brilliant idea of bifocals. He cut the lenses from each pair of glasses in half and remade them into a single lens. The top part of the lens would then be used for seeing distances, whereas the bottom part would be used for reading.

Bifocal technology today is of course much more advanced than it was in Franklin's day. But it was Franklin himself, motivated by a need to solve a very personal problem, who laid the groundwork for what would become an invention that, over centuries, has been of great benefit to millions of people the world over.

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Benjamin Franklin (1706-1790), one of the Founding Fathers as well as an author, printer, and scientist, invented bifocals because he suffered from presbyopia, a condition that means "age of sight" and that makes it harder for the eye to adjust to seeing objects at different distances as one ages. He had suffered from vision problems for a long time, probably dating back to the 1730s, and a print from 1764 shows Franklin wearing an usual pair of glasses that are likely bifocals. While Franklin was in Paris serving as the American envoy to the court of Louis XVI, Franklin wrote a letter dated August 21, 1784 to his friend George Whatley that read, "I cannot distinguish a letter even of large print; but am happy in the invention of double spectacles, which serving for distant objects as well as near ones, make my eyes as useful to me as ever they were.” This letter suggests that Franklin had already invented bifocals.

Bifocals have an upper part (which is less convex) that allows people to see objects at a distance and a lower part (which is more convex) that allows people to read. During Franklin's time, it was difficult for glassmakers to cut two separate lenses to make bifocals and to fuse them together in the same frame. Franklin also made several discoveries related to electricity. 



Last Updated by eNotes Editorial on
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