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How Do I Read My Prescription?An eyeglass prescription is written in a standardized format however sometimes they can be hard to understand. Here are what the numbers mean:
Right and Left Eye
The letters OD (usually the top line of your prescription) and OS (usually the bottom line) in front of a prescription let us know which eye each row of numbers is for.
OD (Oculus Dexter) = right eye
OS (Oculus Sinister) = left eye
OU (Oculus Uterque, Oculus Unitas or Oculus Uniter) = both eyes.
(Note - PL = PLANO; a placeholder for the number zero // DS also = zero)
SPH - Sphere or Spherical
The first number in the prescription is the Sphere (or Spherical) and it is the spherical refractive error (farsightedness or nearsightedness). When there is a minus sign in front of the SPH number, the patient is nearsighted (meaning they would need glasses to see things that were far away like the TV). A plus sign would indicate someone who was farsighted (meaning they had trouble reading a menu or their watch). So then, People who are Nearsighted would need “distance” glasses, and people who are Farsighted would need “reading” glasses
CYL – Cylinder
The second number in the prescription is the Cylinder and it is used to indicate a correction for astigmatism. (An eye that is no longer round but more like an egg or football shape). If there is no astigmatism, you may see a zero or the letters DS or SPH after the first number to let the optician know that the doctor didn’t just forget to write in the astigmatism. (note: -75 = -0.75 // +125 = +1.25) If your prescription does not have an astigmatism correction just choose zero
The last number in a basic prescription is the Axis or direction of the astigmatism. Astigmatism, a football-shaped eye, can be measured in any direction around the clock. The Axis numbers indicate the orientation of the football shape. (note: X = axis – sometimes written as X 80 or AXIS 080 - - - - the number “80” is just used for this example, your number will probably be different)
There may be additional numbers in a glasses prescription. The ADD numbers denote the amount of power that gets added to the distance prescription (SPH) and is used to create your “reading-only” prescription for “readers” - or for the lower portion of bifocal and progressive lenses.
Note: Sometimes you might have a prescription that has “NV” on it. This means it is for Near Vision – or in other words....for reading glasses or “readers”. This means that the SPH power and the ADD power have already been added together by your doctor for your readers.
Otherwise it would be a “DV” prescription Distance Vision prescription and, if you wanted to make “readers” out of them, there would be an ADD number and our lab would do the addition to get reading glasses instead of distance glasses.
If there is only one ADD power on your prescription for bifocals, this means that the same ADD power is used for both eyes. If there is no ADD power given, leave this section blank when ordering.
A Prism correction is used to treat muscular imbalance or other conditions and the numbers are usually left blank on the prescription and not many people need this correction. Sometimes, if the basic prescription is followed by a small number with a superscript (1^) it indicates prism correction. There may be more than one set of prism numbers for each eye
NOTE ON ENTERING YOUR PRESCRIPTION INFO: Very importantly, pay close attention to plus and minus sign as this will greatly affect the lens. If there is anything on the prescription you are not familiar, please call our Customer Service and we will be happy to assist you.
ALSO VERY IMPORTANT - - When choosing frames for bifocal or progressive lenses, you must have a lens height of at least 28mm. It is for this reason that our site blocks sizes smaller than 28mm so you cant make a mistake.
The following are a few examples of sample prescriptions:
Note that each of the following examples is for the same eyeglasses prescription. Also note that the ADD, which is for the reading portion of a bifocal or progressive lens is not in the last example because there is a separate NV or Near Vision portion for this prescription.
Here is some more detail on prescriptions if you like.........
On a typical prescription, you will see two sets of rows. Most of the time top portion is for your OD or right eye while the bottom portion is for your OS or left eye.