Prescription (Rx) Help - Understanding your Rx

Help Topics

About Your Prescription (Rx)

Your prescription provides us with your doctor's recommendation for clear and comfortable vision. Please take a brief moment now to review your information with our 3 samples shown here. They represent 3 different ways of writing the same prescription:

Note, particularly:

  1. Your astigmatism correction ("cylinder"). Some doctors write their prescriptions in plus (+) cylinder and some in minus (-) cylinder. They are not the same. Take special note of this when entering your prescription later. If you don't see anything there, leave it blank.
  2. "dist" (distance) is often abbreviated "D.V."
  3. "near" (reading) is often abbreviated "N.V."
  4. For reading-only glasses: Some doctors will write the reading prescription separately, in its entirety (as "NEAR" or "N.V." or "N.V.O."), as in SAMPLE Rx #3. If this is the case, enter the power in the BOTTOM half of the form (you'll see; it's easy), and leave the ADD power blank ("0.00").

If you do not understand ANY part of your prescription, please call us to ensure everything is entered correctly. Don't be shy; we are here to help, and we want your glasses to be made exactly to your doctor's specifications.

OD= Right Eye
OS=Left Eye
OU = Both Eyes

Other Helpful Hints:

  1. Your doctor may use a blank Rx pad, not a pre-made Rx pad for eyeglasses only. If this is the case, you can draw imaginary grid-lines to separate the numbers. It will separate the different values more easily for you. The top power is always the right eye & the bottom power is always the left.
  2. If you don't see numbers in some of the boxes (if there is no CYL or AXIS or ADD), leave those values blank when ordering. If you only see one number for each eye, it's the "SPHERE" power; leave all the other fields blank.
  3. It is common for the doctor to sometimes leave out the decimal points. If you see a number like -25 or +175, it is understood that your doctor means -0.25 or +1.75, respectively. Also, an axis of 5 (or 05) is the same as 005; 90 is the same as 090. It's like using abbreviations or writing in short-hand.
  4. If you have no astigmatism in one or both eyes, your doctor may just write the sphere power alone, or may use placeholders like sph ("sphere") or D.S. ("diopters sphere") instead.
  5. If you have a prescription for bifocals, and you only see one ADD power, it's understood that you have the same ADD for both eyes. If you don't see an ADD power, leave it blank.
  6. Some common prescription abbreviations:

    SPH or sph = SPHERE power; the "overall" power

    D.S. or DS = diopters sphere (means you have sphere power only)

    CYL or cyl = CYLINDER power; the amount of astigmatism

    X = axis; X 90 means AXIS 090

    ADD = how much power gets added to the distance Rx, for your reading-only Rx
        or for the bottom half of your bifocals/progressives

    Pl or pl or plo = PLANO; it's a placeholder for the number zero

    O.D. or OD = right eye

    O.S. or OS = left eye

    O.U. or OU = both eyes

    NV or NVO = near-vision or near-vision-only; your doctor is recommending "reading-only" glasses

    P.D. or PD = pupillary distance (the distance in between your right pupil and your left pupil), in millimeters (mm)

    -50 = -0.50

    +100 = +1.00

If you still do not understand ANY part of your prescription, please contact us to ensure everything is entered correctly. Don't be shy; we are here to help, and we want your glasses to be made exactly to your doctor's specifications.

Your Pupillary Distance (P.D.)

This measurement is necessary to ensure the correct positioning of your lenses within the frame you have chosen. Have a friend* measure the distance from the center of the pupil (black dot) in one eye to the center of the pupil in the other eye. It's like measuring a line connecting the two black dots.

To measure your PD:

  1. Place the millimeter ruler on the bridge of your nose.
  2. Have a friend face you about arms length away.
  3. Have your friend measure the distance between the center of your pupils (the black dots in the middle of your eyes).
  4. (Or you can do it yourself simply by looking in the mirror).

You can also get this information from your doctor or from a licensed optician.

As a guideline:

  • Most adults' PD's are between 55-65.
  • Most kids' PD's are between 42-54.

Download a printable ruler here (pdf).

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* NY and MA residents must have their PD measured by a doctor or licensed optician.

If you had your PD measured for you but there's more than one number:

If you have two different numbers, you have either been given both the Distance/Reading or Right Eye/Left Eye:

  • If the numbers are higher (and different), like 62/59, then the first number is your Distance PD and the second is your Near PD (for reading-only glasses).
  • If the two numbers are lower (and different), like 30.5/31.5, then you had someone take your PD one eye at a time (called "monocular PD"). The first number is for the right eye (O.D.) and the second number is for the left eye (O.S.). If you have a monocular PD available, put it in the "Customer notes" section of the order form and we'll use it.
  • If the two numbers are the same, like 30.5/30.5, you can just add them together (61 in this example) and we'll automatically divide it equally.