When you
leave Carolina Ophthalmology with a new glasses prescription, it can be helpful
to understand what the numbers indicate about the glasses you need and about
your eyesight. When you look at the prescription, you will see two sets of
numbers under the headings of OD and OS. They are abbreviations from the Latin
forms of right and left eye.
OD (Oculus Dextrus)
means right eye
OS (Oculus Sinister)
means left eye
Without Astigmatism:
For people
who have no astigmatism (spherical eyes), there will be one number for each eye. This number is
known as the sphere portion of the prescription. The farther away
from zero this number is, the worse your eyesight is, and the more correction
your lenses will employ. A plus sign in front of this number indicates you are
farsighted (need glasses to see up close) and a minus sign in front of the
number indicates you are nearsighted (need glasses to see far away). The number
shows how many diopters, units that measure correction, your lens requires.
For example,
if your glasses prescription read:
OD: -1.50
OS: -2.75
That would
mean that your right eye has 1.50 diopters of nearsightedness and your left eye
has 2.75. Another way to say it is that your right eye requires -1.50 diopters
of correction and your left requires -2.75.
This
indicates that you are nearsighted, and that your left eye requires more correction
than your right.
With Astigmatism:
For people
who have astigmatism (non-spherical eyes), there will be three numbers for
each eye in your prescription.
The first
number is the sphere, which is the number discussed above.
This is the degree of nearsightedness or farsightedness.
The second
number is the cylinder. This represents the amount of astigmatism
measured in diopters. This can be a positive or negative number based on which
type of measurement system your doctor uses. At Carolina Ophthalmology, we
measure in plus cylinder, so it will have a plus sign in front of it. The
bigger the number, the more astigmatism your eye has.
The third
number is the axis. This number will be somewhere between 0 and 180 and
is measured in degrees. It represents the orientation of your astigmatism.
For example,
if your glasses prescription read:
OD: -3.00 +1.50
x 045
OS: -3.50 +2.00
x 105
That would mean
that your right eye has 3.00 diopters of nearsightedness with 1.50 diopters of
astigmatism at an axis of 45 degrees. Your left eye has 3.50 diopters of
nearsightedness with 2.00 diopters of astigmatism at 105 degrees.
Your left
eye would require more correction than your right. It has both more nearsightedness
and more astigmatism.
Call us
today to schedule an appointment to come in and get a new glasses prescription!
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