What are bifocals?
The bifocal is a special type of glasses, in that it has both types of lens grafted into it. In the Franklin style, the bifocal would have the upper pane of glass in a close to concave shape while the more convex of the glass would be in the lower half of the pair. The bifocal can correct sight range issues due to conditions such as presbyopia, a condition of farsightedness that typically afflicts the middling and older ages.