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Bifocal Lenses |
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The bifocal lens, also called Franklin and split
bifocal, was first invented by Benjamin Franklin in the 18th
century.
Multifocal lenses are commonly used to accommodate
Presbyopia patients. The
bifocal is the most basic multifocal lens. This lens consists of two prescriptions; usually a distance
prescription with a reading addition placed in a lower segment.
Since the basic split bifocal design, the bifocal has adapted many
different lens designs to accommodate different preferences. Some
include the Flat Tops, Round Segments, Curve Tops,
Executives,
Ultex and the Blended Bifocal. Through the evolution
of the bifocal there have been many styles added and discontinued.
Below you will find several different types of bifocal
lenses
along with characteristics to accommodate different
lifestyles and needs. |
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Flat Top |
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The
flat top is also called the ”D” style multifocal lens. This design has
a segment width that ranges from 25mm to 45mm. The Flat Top is
regarded as one of the easiest multifocal lenses to adapt to, hence
it is the most commonly used bifocal (FT 28mm is referred to as the
standard size). This
lens style is also one of the most readily available in almost any medium
and including comfort lenses (ie. Polarized and Transition)
(make a link for mediums). The Flat Top utilizes the complete
width of the segment giving the user a definitive reading and
distance
transition |
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Round Top |
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This lens is also called a CFR (Croma Free Round - In reference to
the glass fused lenses), and a kryptok lens. This lens has been
offered in widths ranges including 22, 25 and 28mm, however some
sizes and mediums in this lens have been phased out and are no
longer available. This lens gives the user a narrower initial
reading range up top, because of its round top. |
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Curve
Top |
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Also called the C-Style Segment, this lens has been offered in
widths of 28,35 and 45mm. Like the round top some sizes and mediums
in this lens have been phased out and are no longer available. Since
the Flat Top was initially patented. it has been said that the curve
top was a way to reach the bifocal market without consequence to
patent infringement. This design's rounded corners on the bifocal
segment have been promoted to enhance peripheral vision. |
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Executives |
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This lens is the closest to the original bifocal. The Executive lens
is also know as the Franklin, Dual Lens, Diplomat, Bi-Field and Full
Segment. This lens is often recommended as an occupational lens for
patients involved with a lot of reading. This style segment offers
the widest reading range of any of the bifocals for obvious reasons.
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Ultex |
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The Ultex lens has been phased out in many mediums. This lens is also
called the Baseball Segment and CX. The segment usually measures
38mm in width. The Ultex lens is another recommended occupational
lens offering a vast reading range. The wide round segment allows
for more peripheral vision. |
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Blended |
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The Blended bifocal is also called the Invisible Bifocal,
Seamless, Blended 28 and the Younger. The segment width of the
Blended bifocal is 28mm. This lens design is Cosmetically the best
looking lens of all the bifocals, showing virtually no sign of a
segment. However, there is a 1 to 2mm blending range between the
segment power and the lens prescription. This blending range has a
distorted perspective that can prove to be non-adaptable for some
patients. |
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All images and
literature above are Copy written by Solis Inc. Any use
with out the written consent
of Solis Inc. is strictly prohibited. |
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All literature on
this website is strictly for reference. Specifications
for individual needs may vary. Please consult with a
doctor or licensed Optician to accommodate individual
needs. |
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