Trifocals are eyeglasses with lenses that have three regions which correct for distance, intermediate (arm's length), and near vision.
[1] Trifocals are mostly used by people with advanced presbyopia who have been prescribed 2 diopters or more of reading addition.
Trifocal lenses are made in similar styles to bifocals, but with an additional segment for intermediate vision above the reading section.
Larger intermediate segments are available, and are particularly useful for people who spend a lot of time using computers.
Trifocals are becoming rarer as more people choose to wear progressive lenses.