How to Read Your Child's Prescription


Finding out your child needs glasses is overwhelming. Then trying to read their prescription?

That’s a whole other story.

"I was overwhelmed with new terminology and her diagnosis (hyperopia anisometropia). Even though I worked in an optometrist office in college, I still did not understand the difference between PD, OD, and OS."

- Cassie Sperling

When you understand your child’s prescription, you can better understand your child’s vision.

We have put together a cheat sheet guide on understanding your child's prescription to help make better sense of their eye condition and why they need glasses.

Step 1: OS versus OD

OS (oculus sinister) means the left eye

OD (oculus dextrus) means the right eye

Step 2: SPHERE (abbreviated as SPH)

Sphere describes the degree of nearsightedness or farsightedness

(-) child is nearsighted: myopia

(+) child is farsighted: hyeropia

0, pl, Plano: no error

KEY TIP: the further away from zero the number on your child’s prescription, the more vision correction your child needs.

Step 3: CYLINDER (abbreviated as CYL) and AXIS

Cylinder is the measure of astigmatism, meaning the front of the eye has less of a perfectly round shape

KEY TIP: If your child has astigmatism, they do not see clearly either at a distance or near, which can result in blurry vision & frequent headaches.

Some prescriptions may not need astigmatism correction - your doctor may just write sphere power or use (SPH) or DS (diopters sphere)

AXIS  The axis indicates the orientation of astigmatism, measured in degrees from 1 to 180 .

If you do have a CYL number you will also have an axis number.


ADD (ADDITION) is used with multifocal lenses (ie bifocals)

It is an additional magnification which helps with vision at close range.

Ex. If your child needs bifocals, you will likely see a number here.

**We cannot fill prescriptions that require a bifocal. If you see this on your prescription, please contact us at and we will make a recommendation for you.


PRISM helps with muscular imbalance in their eyes.

Prism helps to reduce eyestrain and correct double vision.

KEY TIP: We are able to fill prism within a certain range however, there is an additional fee for prescriptions that require a prism.

*Our team will contact you directly if this is listed on your child’s prescription.

PUPILLARY DISTANCE (PD) The distance between the centers of the pupils. This is used to position the lenses in the frame.

KEY TIP: A PD measurement is required in order for us to fill your prescription order.

*If there is not one listed on your child’s prescription, ask your optician. They will have one on file. Or you can also measure your PD yourself using our easy measuring tool.

BINOCULAR pupil-to-pupil measurement. Between 42-60 mm for most children

MONOCULAR per-eye measurement from the pupil to middle of the face.

Example: 25/24.5 - the first number (25) is for the right eye (OD) Second number: (24.5) is for the left eye (OS). Add these two numbers together to get 49.5 binocular.

Need additional help? We’re here to help!

Contact us directly at 

- the JPE team

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