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Prescription Lenses |
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Single
Vision Lenses |
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A single vision lens is a mono visual lens that yields a single
field of vision, whether there is no prescription or a
single RX prescription.
A
single vision prescription lens may consist of two
physical elements of correction. The two elements are a
sphere and a cylinder, which are measured in
diopters. The sphere
is primarily used to help
with visual acuity deficiency (nearsighted and
farsighted patients). The cylinder is most commonly
used to treat astigmatism. However,
because of the anatomy of a cylinder, an axis is needed
to identify the cylinders true plane of focus (see image below).
on the other hand, the sphere identifies the element of
correction, whether it is a
minus(-) used to address
nearsightedness or a plus
(+) used to address
farsightedness.
The
sphere and cylinder are both not always needed
simultaneously.
There are many patients that require both a sphere and
cylinder correction with their respective RX
prescription, but it is not uncommon for a patient to
require just one, a sphere correction to address acuity
deficiency or a cylinder correction to just address
astigmatism. |
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Axis
Formats |
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There
are a couple different formats to interpret a cylinder
reading. A minus (-) cylinder is most commonly written
by Optometrist and has become an industry standard from
dispensaries to labs. However, Ophthalmologists more
often than not use a plus (+) cylinder reading when
writing prescriptions. A prescription can generally
look completely different, but yield the same visual
results considering it is the same prescription, whether it is written as a plus (+) cylinder or
minus (-) cylinder (see example below). There is actually a transposition
formula (see formula below) to help interpret a
prescription as a minus (-) or plus (+) cylinder prescription.
Both yielding the same visual effect for a patient and
technically both are the same prescription, but
just prescribed as a plus or minus to accommodate the
doctors preference. |
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Formula |
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First add
the cylinder to the
sphere
=
(+/-
cylinder) +
(+/-
sphere) |
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Then
change the sign of the cylinder to be opposite of its
original sign (+/-) |
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Then
change the axis 90 degrees. (if the axis is less than 90
degrees add 90 degrees to |
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axis, but if it is more than 90 degrees subtract 90
degrees) |
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Example |
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Sph |
Cyl |
Axis |
Transposed would be = |
Sph |
Cyl |
Axis |
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-1.00 |
+1.00 |
X 90 |
Vice Versa |
+/- 0.00 |
-1.00 |
X 180 |
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Multi-focal Lenses |
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A
multifocal lens consist of more than one prescription
within the lens. Early
on, for the most part, the eye only needs a single
prescription to accommodate all visual fields. As the
eye matures the eye loses its elasticity leading to what
is commonly referred to as
presbyopia. This anatomical visual transition
creates a need for a little more prescription to see
objects at close range. The addition of prescription is
referred to as the ADD power. The addition of this add
power to a primary prescription (see single vision above) is
the foundation for a multifocal lens. Multifocal lenses
include progressives, trifocals, bifocals, quadrafocals,
double segments and computer lenses. Below are links to
view characteristics of each respective |
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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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