Your eyeglass prescription may look like a page full of confusing numbers and abbreviations, but it is simply a way of describing how your eyes see.
The good news is that you do not have to memorize what every number means to order glasses with confidence. Understanding the basics can help you feel more comfortable and make sure you are ordering the right lenses.
What do all of these numbers mean?
Most eyeglass prescriptions include a few common measurements.
OD and OS
These simply identify which eye the prescription belongs to.
- OD = Right Eye
- OS = Left Eye
- OU = Both Eyes
Sphere (SPH)
The Sphere number describes whether you are nearsighted or farsighted.
- A minus (-) number means you are nearsighted.
- A plus (+) number means you are farsighted.
The farther the number is from zero, the stronger the prescription.
Cylinder (CYL)
Cylinder measures astigmatism.
Not everyone has a Cylinder value. If yours is blank, you likely do not have measurable astigmatism.
Axis
If your prescription includes a Cylinder value, it will also include an Axis.
The Axis simply tells the lab where your astigmatism correction should be placed. It is measured from 1 to 180 degrees.
ADD
If you wear progressive or bifocal lenses, your prescription may include an ADD value.
This is the additional magnification needed for reading or close-up work.
Is my prescription still valid?
Prescription expiration dates vary by state and by your eye doctor's recommendation.
If your prescription has expired, it is generally a good idea to schedule another eye exam before ordering new glasses. Your vision can change over time, even if your current glasses still seem to work.
Can I use my contact lens prescription?
No.
A contact lens prescription and an eyeglass prescription are not the same.
Because contact lenses sit directly on your eye while glasses sit in front of your face, the measurements are different. Contact lens prescriptions also include information such as base curve and diameter that eyeglass prescriptions do not use.
What if I cannot read my prescription?
Don't worry.
If you are unsure about any part of your prescription, our team is happy to help. We can review it with you before your order is processed and answer any questions you have.
Our goal is for you to understand what you are buying—not just place an order.
The Bottom Line
Your prescription may look complicated, but it is really just a set of measurements that help your lenses provide clear vision.
You do not need to become an expert before ordering glasses. You simply need to understand the basics and know that someone is available if you have questions.
That is exactly why we created the BSE Eyewear Resource Center.