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If
you’re forty or over, chances are you wear some
sort of lens to help you read and see clearly up
close. You may even be wearing a bifocal or
progressive lens to correct distance vision as
well as near. While this certainly works to
solve the problem of farsightedness (also known
as “presbyopia”), it does leave much to be
desired.
Most eyeglass wearers agree that their glasses
work well, but that images begin to blur when
they look away from the center of the lens.
This is a common occurrence that exists mostly
because of the way lenses are designed and the
fact they are mounted in a frame that sits about
ten millimeters away from the eye. For
progressive wearers, the problem is magnified
because there are so many more powers crammed
into the front of the lens (distance,
intermediate and reading).
For decades, progressive lenses have been
considered the “high tech” alternative to the
older bifocal lens, which only offers two
corrective prescriptions (usually distance and
near). The major difference between
progressives and bifocals is in the design of
the lower portion of the lens. The progressive
design uses a changing curve structure to
gradually increase power, while the bifocal
design simply adds a reading only, lined segment
to the bottom of the lens. In both cases, the
optics of the lens is manufactured onto the
front surface of the lens so the back surface
can be manipulated to create a lens with the
prescription required by your doctor
During an examination the eye doctor uses an
instrument called a phoropter. This is the
large instrument that sits in front of the eyes
as the patient reads black letters on a white
background, in a dark room, and sitting in an
upright position. It sits at an exact distance
away from the eye, is horizontally and
vertically flat, and it limits the periphery to
a trial lens that is little more than an inch
wide. This simply cannot be duplicated exactly
when the doctor’s prescription is fabricated
into an eyeglass frame which has curves and
angles that are not as flat and small as the
lenses in a phoropter, and which are worn in
various lighting conditions and during different
body postures. This is why patients often
notice that their vision is somewhat different
with glasses than it was in the exam room.
Unfortunately, there is no way to anticipate how
that prescription lens is going to be positioned
in an eyeglass frame until a frame is actually
selected. And that presents a problem for which
there have been limited solutions. Many
patients – especially those who are wearing
progressives for the first time – complain of a
“swimming” effect as they walk or when their
eyes scan the area in front of them. This
sensation eventually goes away, but often
returns when a new, stronger prescription is
required for a new pair of glasses several years
later.
Now however, thanks to the development of new
technology that does away with the old
manufacturing methods, “digital surfacers” are
allowing the fabrication of lenses that are
unique to each patient and which take posture,
depth and frame angles into consideration.
Digital or “freeform” generators manipulate the
back surface of a lens blank with computerized
methods that plot thousands of points on the
back surface of each lens, like pixels on a
computer screen. This allows a significant
improvement in the peripheral clarity of the
lens and provides more of a high-definition
experience than the old methods allowed. Most
importantly, it more accurately addresses the
requirements of your doctor’s prescription,
which can be mathematically “optimized” to
assure the result intended by the doctor –
despite the curves, angle and size of the
eyeglass frame.
Complementing this new process is a new way of
measuring patients for multifocal lenses. Known
as “centration” devices, these high-tech video
measuring machines give the eyecare practitioner
accurate individualized information for each
unique pair of eyeglasses. By utilizing five
parameters measured by the device, lenses can
now be optimized to produce the best lens
possible for a given prescription/frame
combination.
These parameters are entered into a computer
program, along with the prescription provided by
the doctor, to ascertain an “as worn” (or
optimized) lens power for the patient. All of
the optics for the lens are then digitized onto
the back surface of the lens with the freeform
generator, creating an individualized lens
design that is superior to the designs
previously available. For almost every patient,
this means a more natural and comfortable visual
experience, which is exactly what the doctor ord
Metro Optics Eyewear has invested in the
technology necessary to provide optimized
digital eyewear for patients interested in
obtaining the best visual experience possible.
Each dispensary is equipped with
state-of-the-art centration measuring devices
operated by licensed ophthalmic dispensers who
are fully trained in this new technology.
For further information, stop by one of their
three convenient Bronx
locations or call
1-800-230-EYES and ask how you can digitize your
eyes.
Centration devices like the one above use
high-tech video imagery to capture enhanced
measurements for prescription lens wearers,
providing high definition viewing superior to
older lens designs."s website |
