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Progressive lens
"Zones" |
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Progressive lenses, sometimes referred to as "no-line" bifocals,
provide vision correction for the three basic vision zones
- distance vision,
intermediate vision, and near vision. Because
they provide vision in these three zones, they are often thought of as a
type of trifocal.
In reality, progressive lenses are neither a type of bifocal or trifocal
- they are "aspheric" in design, which means the curvature (and focusing
power) gradually changes from the top of the lens to the bottom. It is
this gradual change or "progression" in power from top
to bottom that gives rise to the name "progressive." |
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Progressive lenses provide a great
solution for many people who find their present lens design limits
their vision for a particular distance or activity.
Progressives offer a range of vision as close to natural
as can be obtained from prescription eyeglasses. They
provide clearer vision not just for distance, intermediate and near
but also for all distances in between. Because there is no abrupt
change of power in the lens, there are no visible dividing lines.
The distance zone of the lens allows you to see objects from a few
feet away to as far as your eye can see. The mid-range portion of the lens
("progression corridor") allows you to clearly see
anything at an arm's length, such as your computer screen, objects on your desk,
or items on a shelf at the supermarket. The lowest part of the lens,
the near zone, allows you to see up close. The design of progressive
lenses also allows a more natural and relaxed head posture when
viewing objects at slightly longer reading distances, such as
a newspaper or computer screen.
More
Options - A variety of progressive lens designs are
available today. Some progressives are designed with a wider
intermediate zone to work especially well for computer use. Others
have a larger reading zone. In the past, a larger frame was often
required when selecting progressive lenses. If a frame was too
small, a large portion of the near zone was
removed when cutting the lens to fit the frame. Many lens
manufacturers now offer "compact" progressive designs that work
very well
with smaller frames. Progressives are available in glass, plastic,
polycarbonate, and
photochromic (light-sensitive) lenses.
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Distance Zone |
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Intermediate Zone |
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Near Zone |
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