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Mulitfocal Lenses: Bifocals and
Trifocals
Multifocal lenses have multiple uses, so that you can see
objects at varying distances using different lens corrections.
A bifocal offers two different viewing fields (near and
far). Progressives and trifocals offer three different viewing
fields (near, arms-length, and far). Bifocals and trifocals
have visible lines that separate the different areas of
the lens. A progressive lens is a trifocal lens without
lines; the top portion of the lens if for viewing distance
objects, the middle section is for objects at arm's length,
and the bottom section is for reading.
There are three basic types of multifocal lenses:
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Bifocals: provide two vision zones
separated by a visible line. The bottom segment (often
"half-moon" in shape) corrects for near
or reading distances while the remainder of the lens
corrects for distance vision.
Trifocals: offer three vision zones
separated by visible lines. The upper area is for
distance vision, the middle segment provides intermediate
vision for distances between 2 and 7 feet, and the
bottom segment holds the reading prescription.
Progressives: also referred to as
"no-line bifocals". These lenses are similar
to trifocals in that they have 3 different prescription
areas for near, intermediate, and distance vision.
Progressives differ from bifocals and trifocals in
that the different zones are not separated by visible
lines, but rather offer a natural, "progressive",
transition between the different powers on the lens.
This eliminates the problem of "image jump"
associated with lined multifocals and presents a more
attractive appearance.
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Your eye doctor will discuss the benefits of these choices
with you during your eye exam. However, you should make
this decision based on your own lifestyle. Multifocal lenses
are convenient because you don't need to remove or change
eyeglasses in order to read.
Some people prefer progressive lenses because they do not
like other people to see the line
Getting accustomed to this kind of lens can be difficult,
and you must have proper instruction by an eyecare professional.
For example, the way to use multifocal lenses is to look
down with your eyes, not with your head.
Nowadays, multifocal wearers have lots of options. They
include special glasses for computers and other tasks that
take place at the intermediate range, as well as lenses
for reading distance and special combinations for unique
work situations. You should ask you eye doctor which lens
option is right for you.
Visit our
eyeglass guide for additional information
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