Knowing how to read your child’s eyeglass prescription is important. While you may already know whether your child is nearsighted, farsighted, or has astigmatism, understanding those details on the prescription itself can feel confusing. That’s why we’ve created a simple guide to help parents read a glasses prescription easily—so you can order your child’s new glasses with confidence and without delay.
If your child has had an eye exam and their vision needs have changed, it’s important to order new prescription glasses as soon as possible. Your child’s updated prescription from their optometrist or ophthalmologist provides all the information needed to do that.
Most online eyewear retailers will ask you to enter the prescription details during checkout. If you’re not familiar with how to read a prescription, this step can feel confusing—which is why understanding each part of it makes the process much easier.
What do all these letters and numbers mean?
The numbers on your child’s eyeglass prescription show exactly how the lenses should be made for clear vision. Below, we explain common terms like SPH, CYL, Axis, Prism, and PD to help parents understand their child’s prescription with confidence.
OS and OD meaning
OD comes from the Latin term oculus dexter, which means the right eye.
OS comes from oculus sinister, meaning the left eye. These terms are commonly used on eyeglass prescriptions.
OU is short for oculus uterque, which means both eyes. This helps parents quickly understand which eye each prescription value refers to.
Sphere, Cylinder, and Axis
Sphere (SPH)
This number shows how strong the lenses need to be for your child to see clearly. A minus (–) sign means your child is nearsighted, while a plus (+) sign means they are farsighted.
Cylinder (CYL)
This number is used to correct astigmatism. If this section is left blank, it means your child does not have astigmatism.
Axis
If your child has astigmatism, the axis number shows the direction the lens power is applied to properly correct it.
ADD or NV value
If your child has a multifocal prescription, you’ll see an ADD value, sometimes labeled NV. This number shows the additional lens strength needed to help your child see clearly up close.
Prism and base values
If your child’s prescription is used to correct eye alignment issues, it will include PRISM and BASE values. These numbers tell us how to shape the lenses to help properly align your child’s vision.
The base value may say “in” or “out,” or “up” and “down,” showing the direction the prism needs to be placed.
How often should your kids get an eye exam?
Children should have their first eye exam when they are around six months old, and then another just before they start school. This ensures that they can see clearly in class; poor vision can seriously impact a child’s learning.