What Are Bifocal Lenses?
Widely known as ‘Benjamin Franklin glasses’, (he did, after all, invent them), bifocals have made a huge impact on the eyewear industry. Bifocal glasses have two separate optical powers, or in more simple terms, have lenses with two areas: one larger area to view objects further away, and one smaller area at the bottom to see nearby objects, for example reading a book. There are noticeable lines that separate the two optical powers and the part of the lens designed to view nearby objects is particularly visible. This area is like a built in magnifying glass and thicker than the rest of the lens.
Advantages And Disadvantages Of Bifocals
Advantages of bifocals:
You don’t need to carry around a separate pair of reading glasses.
They are typically less expensive than progressive lenses.
Disadvantages of bifocals:
The visible separation between the two viewing areas can look unfashionable or be annoying to wear.
They are an outdated version of multifocal glasses.
Bifocals stuck out because they had a line dividing the lens in two; the upper half was for distance vision, and the lower for close-range vision. To many people, these were considered ugly and could even be less convenient than two separate pairs of glasses, as wearers would suffer from “image jump” when their focus flickered between the two halves of the lens.
Progressive lenses, however, eliminate this uncomfortable jump by having a smooth and consistent gradient between the differing lens powers. This is why they are also sometimes referred to as multi- or vari-focal lenses, because they offer all of the advantages of classic bifocal lenses without the inconvenience or cosmetic drawbacks.