Bifocals

Bifocals are eyeglasses with two distinct optical powers. Bifocals are most commonly prescribed to people with presbyopia who also require a correction for myopia, hypermetropia, and/or astigmatism. Benjamin Franklin is usually credited with the creation of the first pair of bifocals in the early 1760s, though the first indication of this comes from a political cartoon printed in 1764. A great number of letters and publications from that time per... more

Bifocals are eyeglasses with two distinct optical powers. Bifocals are most commonly prescribed to people with presbyopia who also require a correction for myopia, hypermetropia, and/or astigmatism. Benjamin Franklin is usually credited with the creation of the first pair of bifocals in the early 1760s, though the first indication of this comes from a political cartoon printed in 1764. A great number of letters and publications from that time period refer to Dr. Franklin's spectacles, including his first reference to them in a letter dated July 22, 1785. John Isaac Hawkins, the inventor of trifocal lenses, coined the term bifocals in 1824 and credited Dr. Franklin. Franklin's original bifocals were designed with the most convex lenses (for close viewing) in the lower half of the frame and the least convex lenses on the upper. Up until the beginning of the 20th century two separate lenses were cut in half and combined together in the rim of the frame. The mounting of two half lenses... less