Bifocal lenses are lenses with two reading areas, that are separated by a visible line, which distinguishes these lenses from the new progressive lines which do not have a visible line. The most common bifocal lenses are designed with a half-moon shaped reading area in the bottom half of the lens, called a "flat top".
Some people prefer the "executive" or “Franklin” style, in which the lens is bisected by a horizontal line across the entire width of the lens, but unfortunately, those lenses were permanently discontinued by all lens makers in 2023. We supply the flat top 28 unless you specify otherwise. Bifocal lenses are the most cost effective way to create a lens with two viewing areas. In the past, most bifocal lenses were made with a distance and a reading area; nowadays, people are making bifocals with an intermediate area for computer and pad use, together with either a distance area or a reading area.