Trying to read a lens prescription can be confusing and you need to get the formula right so we can make the best pair of glasses for you. On your script you will have a sphere (to indicate the strength of the lens you need), a cylinder (which indicates the lens power needed to correct astigmatism), and an axis (which indicates where to place the lens correction for astigmatism), among a few other details.
The most common prescription format is in the way of a grid with clearly printed fields for OD, OS, SPH, CYL, etc.; values are usually entered with computer, but may be handwritten by doctor.
Sphere (SPH) and Cylinder (CYL) always have a (+) or (-) sign.
On any prescription, PD can be written in different ways: e.g., 62 (Single PD), 33/31 (Dual PD), or 62/60 (Distance PD/Near PD).
For multi-focal glasses, as well as reading and computer glasses, your Rx will include an ADD or NV value. This number always has a (+) sign.
The type of Rx glasses may be noted on a prescription, such as DV [Distance Vision/nearsightedness] and NV [Near Vision/reading].
What if I have PLANO/PL under SPH?
If there is "Plano" or "PL" in the SPH section of your prescription, it means no nearsighted or farsighted correction is needed. Enter 0 for your value wizard.
What if I have SPHERE/SPH/S/DS under CYL?
If there is "DS" or "Sph" or "Spherical" in the Cylinder space it indicates no correction is needed. Enter 0 for your value in the wizard.
What if I have 2 ADD values?
If you have two ADD values in your prescription (i.e.- ADD +2.00 and ADD +2.25 PAL), the ADD value with PAL (i.e.- 2.25) should be entered into the wizard ADD section.
Check out the following glossary for even more details on what the numbers in your eyeglasses prescription mean:
1. OD (Oculus Dexter), OS (Oculus Sinister)
OD and OS are key to reading any eyeglasses prescription, regardless of the correction type. Sometimes appearing as O.D. and O.S., they are Latin abbreviations for right eye (OD) and left eye (OS). Some doctors may use OU to reference both eyes. And sometimes you will see RE and LE for right eye and left eye respectively.
2. SPH (Sphere)
Measured in diopters, the SPH number refers to the lens power necessary for each eye. A minus (-) is used to correct nearsightedness. A plus (+) sign next to the number refers to farsightedness correction.
3. CYL (Cylinder)
CYL is the lens power (also called diopter) used to correct astigmatism. If you have no astigmatism or very slight one, this column will be blank. As with Sphere, a minus indicates lens power for nearsighted astigmatism, a plus indicates farsighted astigmatism.
4. Ax (Axis)
Like CYL, Ax only applies to astigmatism prescriptions. The Ax number refers to angle degrees (1 to 180). If your prescription includes Cylinder lens power, it must include Axis as well.
Only used for multifocal (progressive/bifocal) lenses, ADD refers to the added magnifying power applied to the bottom of the lens in multifocal lenses. PAL is used in some cases by doctors when the addition for progressive lenses is different compared to bifocals.
Prism is used to correct double vision or vision displacement. The Prism value refers to the number of
diopters applied to compensate for image alignment issues. We are not able to accommodate eyeglasses prescriptions that need Prism.
7. PD (Pupillary Distance)
Pupillary distance measures the distance between your pupils. If it's not included in your prescription, you can easily measure it yourself. It's important to measure from the center of one pupil to the center of the other. PD is measured in mm and can be one number like 64 or two numbers like 31/33. The first number in a twonumber PD is the Right or OD. Getting the two-number PD is always the best choice when creating custom made eyewear as it centers each Rx in front of each eye, versus the less accurate method of dividing the single number by two.
- Stand 8-12 inches away from a mirror.
- Hold a ruler against your brow or cheekbones.
- Close your right eye and align the ruler end with the
center of your left pupil.
- Look straight ahead, close your left eye, and open your right eye. Note the measurement to the center of your right pupil.