These lenses are similar to the bifocal lenses in that they provide parts of the lens prescribed to see clearly at multiple distances. They can be lined trifocals, which have distance vision on the top, intermediate or computer vision under the first line, and reading or near vision at the bottom. These glasses have two lines to separate the different parts of the lens.
They can also be “no-line” lenses, also known as progressive addition lenses or no-line bifocals. These lenses offer multiple zones of clarity without any visible lines on the lens. The way the lenses are made allows the power of the lens to gradually fade from distance at the top to intermediate or computer vision in the middle and finally to near vision at the bottom of the lens.