Eyeglass lens with two distinct optical powers invented by Benjamin Franklin
A bifocal lens with areas of differing magnification
Bifocals with separate lenses. In this case, the Swedish ethnologist Jan-Öjvind Swahn [sv].
Bifocals are eyeglasses with two distinct optical powers. Bifocals are commonly prescribed to people with presbyopia who also require a correction for myopia, hyperopia, and/or astigmatism.