How to Read Your Eyeglass Prescription (A Simple Guide)
Your eyeglass prescription can look like a string of random numbers, but it follows a simple layout. Here's what each part means.
Right Eye, Left Eye
• OD = Oculus Dexter = right eye
• OS = Oculus Sinister = left eye
• OU = Oculus Uterque = both eyes
Some prescriptions simply say "Right" and "Left" instead.
SPH (Sphere)
This is the main strength of your lens.
• Minus (-) means you're nearsighted. You see well up close but distant objects are blurry.
• Plus (+) means you're farsighted. Close-up objects are harder to see.
The bigger the number, the stronger the prescription. If you see "PL" or "Plano," that means "needs no correction".
CYL (Cylinder)
This corrects astigmatism, which happens when the eye's surface is shaped more like a football than a basketball. If this box is blank, you don't have astigmatism, or it's too mild to correct.
Axis
If you have a CYL value, you'll also have an Axis. It's a number from 1 to 180 that tells the lab which direction to place the astigmatism correction. It's an orientation, not a strength, so a higher number doesn't mean a stronger prescription.
ADD (Addition)
This is additional magnifying power for reading, and it’s typically prescribed for people over 40. You might use it in single vision lenses made just for near work, like reading glasses, or in progressive lenses, which combine your distance and reading prescriptions in one pair.
Prism
Less common. Prism corrects eye alignment problems. If your prescription includes prism, you'll see a value and a direction (such as "BU" for base up or "BI" for base in).
What About PD?
Your pupillary distance (PD) is the distance between the centers of your pupils, measured in millimeters. It's often left off prescriptions, but you'll need it to order glasses online. You can ask your eye doctor for it or measure it at home.
Quick Example
|
Eye |
SPH |
CYL |
Axis |
ADD |
|
OD |
-2.25 |
-0.75 |
180 |
+2.00 |
|
OS |
-2.00 |
-0.50 |
175 |
+2.00 |
This person is nearsighted in both eyes, has mild astigmatism, and needs reading power, making them a good candidate for progressive lenses.
Check the Date
Most eyeglass prescriptions expire after one to two years, depending on your state and your doctor. If yours is out of date, schedule an eye exam before ordering.
Question about your prescription?
Have questions about your prescription? We’re happy to help. Contact us, Monday through Friday 10 AM–6 PM and Saturday 11 AM–4 PM, and a board-certified optician will walk you through it before you order.
At Peek Eyewear, you can upload a photo of your prescription at checkout, or email it to us later. Every lens is cut in our own USA lab, and prescription glasses start at $95 with frame and single vision lenses included.
