Our Multifocal Lenses
At CLA we have a variety of different
contact lenses. Your fitter is most qualified
to determine which is the right one for
you. Here are a few examples:
1. Rigid Gas Permeable
Multifocals
An annular, aspheric bifocal lens. Annular means that the
center portion of the lens is devoted
to distance vision, while the outer portion
deals with the near or reading power.
Aspheric refers to the unique curvature
on the back surface of the lens which
is known as the “EQ”. The EQ
is the outer portion of the lens where
the curvature of the lens is chosen so
the lens aligns comfortably with the mid-peripheral
region of the cornea.
Parameters
The latitude is available in powers
from + 12.00 to – 20.00 with add
powers from + 1.75 to + 3.00 in 0.25 D.
steps.
These lenses correct most corneal astigmatism.
2. Bifocal
A very special type of rigid gas permeable
contact lens. In terms
of lens curvature, the lens surface is
mostly spherical, meaning that it is just
the common everyday simple shape. It is
the way these curvatures are arranged
which makes the lens unique.
The distance portion of the lens makes
up 70% of the total area while the inferior
area of the lens is mostly near or reading
power. Above this is the very small but
necessary intermediate zone which allows
the wearer to see between reading and
distance zones. These lenses are also
prism ballasted which simply means the
lens is thicker and has more weight inferiorly
for stabilization reasons.
Parameters
The <1--Presbylite--> bifocal lens is available
in distance powers from + 20.00 D. to
– 20.00 D. Add or reading powers
begin at + 1.50 and extend to + 3.00 D.
These lenses correct most corneal astigmatism.
Soft Lens Multifocals
3. Multifocals
A well hydrated, very comfortable bifocal
lens. Based on a modified annular lens principle
but rather than having BOTH lenses with
the distance portion in the center and
the reading at the periphery, these lenses
reverse the procedure from one another.
In other words, one eye has distance in
the center / reading in the periphery
while the other is opposite that. The
reading is in the center while the distance
is now in the periphery.
In the same sense that one uses one hand
more than the other, this sytle applies
the same principle to the contact lens where
one eye is more dominant than the other.
The dominant eye is the eye which receives
the lens with the distance vision in the
middle and the reading portion in the
outer region. The other eye adapts to
near vision. The beauty of this system
lies in the fact that should either your
reading or distance not be what is deemed
satisfactory, we at CLA can modify either
lens to bring the wearer to their maximum
acceptable level of vision.
Parameters
The multifocal contact lens is available
in powers from + 20.00 to – 20.00
D.for distance and + 1.00 to + 4.00 D.
for reading.
This lens is also available with astigmatism
corrections.
4. Multifocal
These designs are a multi-aspheric
which means there are different curvatures
on the lens as opposed to the spherical
design which basically has one curvature.
This muti-asphericity is necessary to
help the wearer see at many different
distances. The counterpart to this lens
in eyeglasses is the progressive addition
lens which millions are now wearing to
deal with Presbyopia. Presbyopia is a
condition which results in both men and
women over the age of forty-five. As we
age, we are unable to accommodate; objects
we are looking at closely must be moved
further and further away the older we
get.
What makes this lens different
from other lenses? It is the accommodation
zone. The accommodation zone restores
natural accommodation by creating a small
area of over magnification over the near
vision correction needed. In other words,
it is stronger in power than the reading
add power which enables the wearer to
focus clearly on objects previously distorted
due to presbyopia. The lens comes in two
different near diameters: 1.5 and 1.9
mm. Your eye care professional at CLA
will choose the best size for you.
Parameters
The Multifocal contact lenses
are available from + 8.00 to – 10.00
D. for distance and reading add powers
all the way to + 3.25 in the high add
region and + 2.25 in the low add region.
This lens is also available with astigmatism
corrections.
This article was contributed
by Glenn Williams a graduate of Douglas
College’s Dispensing Optician Program
2002
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