What are Bifocals?
Sometimes our vision fails us at two or even three distinct distances,
especially as we age. Bifocal lenses—lenses with two distinct viewing areas—have
traditionally been a reliable solution to such a dilemma. (A lens with three
distinct viewing areas is called a trifocal.)
By distinct, we mean there are noticeable lines separating
the two different fields of vision within a bifocal lens surface. A slight
adjustment to the angle of the head allows wearers to choose which lens area to
look through based on the distance of the object they’re trying to see.
A farsighted person who also has trouble reading may be
prescribed a pair of bifocal reading glasses, for example. The upper section of
the lens would correct difficulties seeing objects at distance, and the lower
section would assist in reading. (Bifocal reading glasses date back to the days
of Benjamin Franklin!)
While wearers quickly adjust to the line separating the
multiple vision fields, it is a noticeable distraction within the lens itself.
This line can be eliminated using a newer lens technology called progressive
lenses.
Progressive lenses incorporate two, three, or more fields of
vision within a single lens without noticeable lens lines. Bifocal, trifocal and
progressive lenses are all considered “multi-focal” lenses—lenses that provide
correction to multiple vision problems.