While traditional multifocal (bifocal and trifocal) lenses have a line in the middle of the lens, progressive lenses are line-free. The power gradually changes from distance correction to intermediate vision (at arm's length), to near vision (at reading distance). Go to Top
a lens that has an infinite number of focal lengths in the central corridor from the distance optical center to the near addition power. A.k.a. lineless bifocal, no-line bifocal, seamless bifocal.