How to Read a Prescription

Breaking Down Your Glasses Prescription

Distance Prescription

Your prescription typically includes a grid with two rows labeled OD (right eye) and OS (left eye). Each eye may have values for Sphere (SPH), Cylinder (CYL), and Axis:

• Sphere (SPH) indicates the strength of your prescription, with positive (+) values for farsightedness and negative (-) values for nearsightedness.
• Cylinder (CYL) and Axis are included if you have astigmatism. Cylinder measures the lens power needed for correction, while Axis (ranging from 0 to 180) specifies the angle.
• If there is no astigmatism correction, Cylinder may be marked as “SPH,” meaning no value is needed.

Bifocal or Progressive Prescription

• If you need correction for both near and far vision, an additional value labeled ADD, Bifocal, or Addition will be present.

• This value is always positive (e.g., +1.25) and indicates the extra magnification required for reading or close-up work.

Pupillary Distance (PD)

• PD measures the distance between your pupils in millimeters and ensures proper lens alignment.
• It may be listed at the top, middle, bottom, or even on the back of your prescription.
• If PD is missing, you can contact your eye doctor or measure it yourself using a ruler.