How to Read an Eyeglass Prescription

Knowing how to read an eyeglass prescription is essential! While you likely know whether you’re nearsighted, farsighted or have astigmatism, determining that from your prescription slip is another thing entirely. That’s why we’ve put together a short guide to help you learn how to read your eye prescription so you can get to ordering your new set of eyeglasses as quickly as possible.


An eye prescription is a document written by an eye doctor, such as an optometrist or ophthalmologist, that specifies the correct eyeglass or contact lens prescription for a person. It typically includes measurements for the eyeglass lenses, including the power and type of lens needed, as well as any special instructions or recommendations. 

An eye prescription typically includes the following information:

  1. Patient's name: This is the name of the person for whom the prescription is written.

  2. Doctor's name: This is the name of the eye doctor who wrote the prescription.

  3. Date of exam: This is the date on which the eye exam was performed.

  4. Type of lens: This indicates whether the prescription is for eyeglasses or contact lenses.

  5. Sphere (SPH): This is the measure of the eyeglass lens power needed to correct nearsightedness or farsightedness. A plus sign (+) indicates a need for a more powerful lens (to correct farsightedness), while a minus sign (-) indicates a need for a less powerful lens (to correct nearsightedness).

  6. Cylinder (CYL): This is the measure of the eyeglass lens power needed to correct astigmatism, a condition in which the eye has an irregular shape.

  7. Axis: This is a measure of the orientation of the cylindrical lens power specified in the CYL value.

  8. Add: This is the additional lens power needed for multifocal lenses (such as bifocals or progressive lenses).

  9. Prism: This is the measure of the lens power needed to correct for certain visual distortions caused by muscle imbalances or other conditions.

  10. Base: This indicates the direction in which the prism power specified in the prism value is oriented.

  11. PD (Pupillary Distance): This is the distance between the centers of the pupils of the eyes, measured in millimeters. This measurement is used to ensure that the eyeglass lenses are properly aligned with the pupils.

  12. Special instructions: This may include any additional notes or recommendations from the eye doctor, such as the need for a special type of lens coating or a specific frame size.

The numbers on your eyeglass prescription describe precisely how your glasses lenses should be cut. Keep your prescription up to date so these numbers can accurately reflect your visual needs. Typically, you’ll see several abbreviations and words labeling all of the important data on your prescription. See below to learn the meaning of SPH, CYL Axis, Prism, PD, and more.

Nearsighted Prescriptions

A nearsighted prescription will feature a number with a minus (-) symbol in the ‘sphere’ box. This means your lenses will be shaped to improve your distance vision.

Farsighted Prescriptions

A prescription for someone who is farsighted will feature a number with a plus (+) symbol in the ‘sphere’ box. This indicates that your lens should be shaped to correct near vision.

Astigmatism Prescriptions

If you have an astigmatism, you will have a number in the ‘cylinder’ column of your prescription that indicates the lens power needed to correct the astigmatism. There will also be a number in the ‘axis’ column that’s needed for astigmatism correction.

Bifocal and Progressive Prescription (Multifocal)

A multifocal prescription will include an ADD value, sometimes marked as NV. This indicates the required strength for the other prescription in your lens.

Prescription with Prism Correction

A prescription for correcting eye alignment issues will include a PRISM and BASE value. These are needed to tell us how to shape the lens so that it can accurately align the wearer’s eyesight. The base value will show either ‘up’ or ‘down’, indicating the direction the prism should be angled.

Pupillary Distance (PD)

How to check your PD

You'll need to know your PD if you want to order glasses from JuJu Optics. Don't worry if your glasses prescription doesn't include your PD, you are able call your eye doctor to retrieve that information.
PD, or pupillary distance, refers to the distance in millimeters between the center of one pupil to the center of the other. Having a correct PD on your glasses prescription insures that you are looking through the ideal spot in your lenses. If this number was not provided on your prescription by your eye care professional, you can measure it yourself.
*Note that the average PD is between 57 and 65mm.
1. Place the ruler directly over the center of your right pupil so that the ruler is horizontal. Place against forehead for added stability. Stand in front of a mirror, or ask someone else to measure for you.
2. While looking straight ahead, measure the distance from the center of your right pupil to the center of your left pupil.
3. Repeat a couple of times for accuracy and use an average for your final measurement.