trifocals

Trifocals are eyeglass lenses that provide three distinct focal powers within a single lens to correct presbyopia. The upper portion is designed for distance vision, the middle portion for intermediate tasks such as computer work, and the lower portion for near tasks like reading. The three zones are usually separated by visible lines, giving the wearer three clearly defined seeing areas.

The concept is traditionally attributed to Benjamin Franklin, who is said to have devised the three-vision lens in the late 18th century. Trifocals became widely used through the 19th and 20th centuries as a practical solution for people needing both distance and near correction, with an intermediate zone added to accommodate mid-range viewing. In contemporary practice, progressive lenses—lenses without visible boundaries—have largely supplanted trifocals in many markets, though trifocals remain available and are still used in some contexts.

Design and manufacture involve shaping a single lens with three optical regions. The top region provides distance power, the middle region offers intermediate power, and the bottom region supplies near power. Because the zones are fixed, users must align their gaze through the appropriate segment, which can require adjustment in head and eye posture. Fitting considerations include segment height, frame choice, and pantoscopic tilt. Some wearers experience abrupt transitions or edge distortion at zone boundaries, contributing to an adaptation period.

Variants include different segment shapes and sizes, with some lenses offering larger intermediate zones. Overall, trifocals represent an older but still valid option for multi-distance vision correction alongside newer alternatives.