Benjamin Franklin invented bifocals in 1784. As announced in a letter to a friend, he called the new invention "double spectacles." The glasses allowed a person to see far or near, depending on what part of the lens they were looking through.
Although Franklin is credited with the invention, historians are unsure if he truly created them or if he had them built by someone else. Franklin ordered specialty eyeglasses while in France on a diplomatic mission in 1779, and he paid a large sum of 18 francs for them, leading some historians to believe these were the bifocals in his letter. Franklin suffered from an eye condition called presbyopia, which makes it difficult for the eye to focus on images up close. Eye doctors prescribe bifocal lenses to patients with this eye condition.