Trifocal lenses are lenses with three reading areas that are separated by a visible line, which distinguishes these lenses from the new progressive lines which do not have a visible line. The most common trifocal lenses are designed with a half-moon shaped reading area in the bottom half of the lens, called a "flat top". However, some people prefer the "executive" or “Franklin” style, in which the lens is bisected by two horizontal line across the entire width of the lens.
Trifocal lenses are the most cost effective way to create a lens with three viewing areas. Trifocal lenses are uncommon now, with the advent of progressive no-line lenses. Trifocal lenses are a good choice for people that are looking for an economical alternative to progressive lenses. Also, many people use trifocal lenses for close up work like fly tying, needlepoint, and other activities that require looking at detailed work. Trifocal lenses are only available in the "flat-top 28" style.