Benjamin Franklin and the Bifocal
How an 18th-century statesman tired of swapping spectacles helped popularise split lenses.
By Lumora Editorial Team · October 2, 2026 · 4 min read
Benjamin Franklin is remembered for electricity experiments, diplomacy and the printing press. He is also widely credited with popularising bifocal spectacles — although, as with many inventions, the full story is a little more complicated.
The problem: two pairs of glasses
As Franklin aged, he found he needed one pair of spectacles for seeing at a distance and another for reading. Constantly switching between them was a nuisance, especially at dinner, where he wanted to see both his plate and the faces of the people he was talking to.
The solution: cut the lenses in half
In a letter written in 1785, Franklin described his solution: he had the lenses of both pairs cut in half and mounted together in a single frame — the distance half on top, the reading half below. Looking straight ahead, he saw far; glancing down, he could read.
He wrote that he found this "more particularly convenient since my being in France", because he could watch people's expressions while they spoke, which helped him understand a language he was still learning.
Did he really invent them?
Historians note that the letter describes Franklin's own use of split lenses, and some argue that opticians in London may have been making similar spectacles around the same time. What is clear is that Franklin's fame and writing helped make the idea well known, and his name has been attached to it ever since.
From split glass to seamless lenses
Early bifocals were literally two pieces of glass held together by the frame. Over the following centuries, makers learned to fuse or mould the reading segment into a single lens, producing the familiar "D"-shaped segment with its visible line.
In the 20th century, progressive lenses arrived. Instead of two distinct zones, power changes gradually from distance at the top to near at the bottom, with an intermediate zone in between and no visible line. Many people now choose progressives, though bifocals remain a practical option for some wearers.
Today's choices
If you have a prescription with an ADD value, you can choose between:
- Bifocal lenses with two distinct zones.
- Progressive lenses that blend distance, intermediate and near.
- Separate reading glasses alongside distance glasses — Franklin's original situation.
Learn how to read the ADD value in our guide to reading a bifocal prescription, or browse frames suitable for progressives.
This article is general information and not a substitute for advice from a licensed eye-care professional.
