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In the
Beginning
 At
the CLMA meeting in Fort Worth, Texas in 1985, the contact lens
manufacturers were asked to develop a Gas Permeable (GP) contact
lens that could compete with the comfort of soft lenses. At that
time, C&H Contact Lens, Inc. began to give this subject serious
thought.
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Reviewing
Design Qualities
After revisiting PMMA and GP designs, we ruled out trying to
tweak a strictly corneal design. However, little to no thought
was given to scleral lens designs because the overall size made
the lenses difficult to handle, and in many cases they were
cosmetically undesirable. A close look at soft lenses revealed
the essence of soft lens comfort: the large diameter combined
with a lens edge that lies close to the sclera. A soft lens
with a diameter smaller than the corneal size will be just as
uncomfortable as a GP. Also, excessive edge standoff in a 15.0
m/m soft lens creates discomfort. |
Unique
Challenges
Now, it became obvious that the answer to comfortable GP fits
would look alot like a soft lens fit. However, the "rigid"
in rigid gas permeable presented some unique challenges: 1. TEAR
EXCHANGE - Soft lenses flex in the peripheral cornea area with
each blink, thus exchanging tears. 2. ALIGNING THE EDGE WITH THE
SCLERA - Draping the lens over the sclera like a soft lens was
out of the question. Therefore, the MacroLens® would have
to match the elevation of the eye in order for the lens to align
with the eye at the center as well as the edge. 3. REMOVING THE
LENS - A 14.0 m/m GP lens with proper alignment for comfort was
almost impossible to remove.
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Implementing Design Attributes
Fifty years ago, Dr. Josef Dallos' research showed that
this type of adherence could be relieved by fenestration.
Noted expert George Meszaros claimed that oxygen around
a fenestration will spread 2.5 times the size of the hole.
So, we thought that if we put eight one millimeter diameter
holes in a circle with an inner circle diameter of ten millimeters,
that the effect would be the same as an 8.5 m/m diameter
corneal lens with an added scleral skirt for comfort. However,
eight holes made the lens cosmetically unacceptable and
fragile. We later found that one hole works better than
eight.
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Patent Issued
Back to research. What was the elevation of the cornea and
how diverse is it? We never found any useable information
on this topic so we had to proceed through trial and error.
This took alot of time and many lens designs. In 1990, we
came to a stop and waited two years for more advanced equipment
to be developed so that we could manufacture a full range
of base curves with consistency. Since we had the new equipment,
we proceeded with our in-house studies and in 1994 filed
for a patent and began selling the MacroLens® in late
1996.
Like
the pioneers of soft lenses, C&H has made design changes
to enhance the ease of fitting for practitioners. Less fitting
time, better quality lenses, and higher DK materials and
an overall more marketable product.
View
U.S. Patent #5,929,968
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Video
Click
here to view a video of the History of the MacroLens.
(Windows® Media Video - 954 KB).
Click here for a free download from Microsoft®.
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