Bifocal lenses contain two optical corrections with a distinct dividing line between the two parts.
The upper part of the lens corrects distance vision and the lower half is for near vision. They’re commonly used by people who have become presbyopic, and need more help with close-up work.
They are also available in three sections, incorporating a correction for intermediate vision. Bifocals and trifocals come in a range of designs but nowadays, varifocal lenses are much more likely to be prescribed.