Bifocals

Bifocals are glasses that have two different strengths of lenses depending on where you look through the lens. Typically bifocals for presbyopia and myopia have the lower section (for use during reading) 1-2 diopters weaker than the upper section. The EM method uses separate differentials and normalized lenses rather than bifocals, making it easier to adjust your lens selections separately.

Multifocals

Multifocals are similar to biofocals, but have a gradual transition between the two lens strengths instead of a distinct line. They may also have a wider variety of available patterns than typical bifocals.