What does my prescription (Rx) mean?

Your prescription or Rx is what an ophthalmologist (an MD) or optometrist (a doctor of optometry) gives you to correct your vision with eyeglasses with corrective lenses. It is used to create the eyeglasses.

Lenses Only - RX

Your prescription has horizontal rows or vertical columns. The top row or first column will always be for your right eye, abbreviated as OD. The second row or column will always be for your left eye, abbreviated as OS.

Each row of the prescription has three main sections: Sphere (SPH)Cylinder (CYL), and AXIS. The SPH section corrects nearsighted or farsighted vision if you have either. The CYL and AXIS sections correct an astigmatism.

There may also be a fourth section on the prescriptionNV-ADD (for Near Vision-Reading ADDition), which could be used to order a pair of bifocal or progressive glasses with a close-up vision section in the bottom part of the lens used for reading.

The SPHCYL, and NV-ADD numbers will always have a plus or minus sign associated with each of them.

Can I get a list of optical abbreviations?

We are happy to provide this list of some optical abbreviations that will help you order your glasses from LensesOnly:


(also NV-ADD): the Near Vision (NV) Reading ADDition correction on a multifocal Rx. This can be used for bifocal or progressive glasses, or for single-vision reading or computer (intermediate) vision glasses.


Lenses Only - Add

Lenses Only - Add

(NOTE: You need an prescription written specifically for eyeglasses; a prescription for contact lenses will not work for eyeglasses!)


Anti-Reflective. A special coating that reduces reflection on the lenses.


the angle at which the Cylinder (CYL) is placed on a lens to correct an astigmatism. Its numerical value ranges from 1 to 180.


If the prescription calls for balance lenses, meaning the same prescription for each eye. Often used when a person has no sight in one eye, so both lenses will have the same thickness.


Refers to a prism correction on your prescription (value may be indicated with Δ, and one of these four abbreviations. The B stands for base, and it could be base down (BD)base in (BI)base out (BO), or base up (BU).


Refers to the Cylinder. Combined with the AXIS, the CYL corrects an astigmatism.


This is the abbreviation for diopter simplex. An eye dr. may write DS on an Rx in the Cylinder (CYL) field if no astigmatism correction is needed.


Refers to distance vision.


Refers to flat-top bifocal.


Refers to near vision.

(also ADD)

The Near Vision (NV) Reading ADDition This is a correction on a multifocal prescription. This can be used for bifocal or progressive glasses, or for single-vision reading or computer (intermediate) vision glasses.


The Latin words for Oculus Dexter, meaning the right eye.


The Latin words for Oculus Sinister, meaning the left eye.


The Latin words for Oculus Uterque, meaning each eye.


Progressive Addition (or AdjustmentLens: sometimes on a Progressive prescription an eye dr. will write two different numbers for the NV-ADD, perhaps +2.25 and +2.50, to increase the reading power in the NV-ADD for Progressive lenses.

Pupillary Distance)

the PD is the measurement of the distance between your pupils. This is important and needed for the manufacturer of the eyeglasses to know where the optical center on each lens will be positioned, so you can see well with the glasses they are making.


The Latin words for “flat.” If this is in the SPH section of an Rx, it means no nearsighted or farsighted correction is needed.


A prescription.


The first section on an prescription. It corrects nearsighted or farsighted vision.


The abbreviation of ultravioletUV light is high frequency and invisible to the human eye. UV light also gives us a sunburn, and too much exposure to it can damage the eye.

(Visual Acuity)

This refers to how well the eye can see. Sometimes this may be written on an prescription, with a number such as 20/20. This would indicate that with eyeglasses made to this prescription, the vision would be corrected to 20/20 vision.

What's pupillary distance (or PD) and how do I get it?

Your pupillary distance (PD) is the measurement of the distance between your pupils.

PD - pupillary distance

This measurement is needed for the manufacturer of the eyeglasses to know where to place the optical center on each lens, so you can see well with the glasses they are making for you.

Am I a single PD or dual PD?

single PD it is the measurement, in millimeters, from the center of one of your pupil to the center of the other.

PD - pupillary distance - single

dual PD is the measurement of the center of each of your pupils to the center of the bridge of your nose.

PD - pupillary distance - dual

Can you fill my strong prescriptions?

We sure can!

Single-vision prescription

Up to -20.00 or +12.00 on the Sphere (SPH)

Up to + or – 6.00 on the Cylinder (CYL)

Bifocal prescription

Up to -9.00 or +6.00 on the SPH

Up to + or – 6.00 on the CYL

Up to +3.50 on the NV-ADD

Progressive prescription

Up to -10.00 or +8.00 on the SPH

Up to + or – 6.00 on the CYL

Up to +3.50 on the NV-ADD

Prism (single-vision only) prescription

Up to 5.00 in any base direction.

What about bifocal or progressive lenses? Do you offer those?

We offer both. If you have ADD or NV-ADD on your prescription, you can get lined bifocals or unlined progressive glasses.

How do I order simple reading glasses?

It is easy to reconfigure a prescription with an NV-ADD for reading. It just involves a little math.

You simply take the NV-ADD number on your prescription and add it to the numbers in your Sphere (SPH) category for each eye. Then lower your distance PD by 3 millimeters if it’s the single PD, by 1.5 millimeters for each eye if it’s the dual PD. That gives you an prescription for single-vision reading glasses!

Lenses Only Reading Glasses How to

Lenses Only Reading Glasses How to

Your New Reading Glasses Rx

Lenses Only Reading Glasses How to

What about prescriptions with prism corrections?

We can make those, for single-vision glasses.

Can I use my contact lens prescription to order eyeglasses?

Sorry, no. A contact lens prescription can only be used for contact lenses.

What do I do if my prescription has expired?

We recommended that you get an eye exam every two years, or even more frequently if you notice that your vision has changed since your last one.