The short answer: Your prescription lists each eye on its own line. OD is your right eye, OS is your left. SPH is the main power, minus for nearsighted and plus for farsighted. CYL and AXIS correct astigmatism. ADD is extra reading power. PD is the distance between your pupils. Together they tell an optician exactly how to grind your lenses.
What each abbreviation means
| Term | Meaning |
|---|---|
| OD (right eye) | From the Latin oculus dexter |
| OS (left eye) | From the Latin oculus sinister |
| OU | Both eyes |
| SPH (sphere) | Main power. Minus is nearsighted, plus is farsighted |
| CYL (cylinder) | Amount of astigmatism correction |
| AXIS | Direction of the astigmatism, 1 to 180 |
| ADD | Added reading power for bifocals or progressives |
| PRISM | Corrects eye alignment, listed only if needed |
| PD | Pupillary distance, in millimeters |
Reading a line, left to right
Take a right-eye line that reads minus 2.00, minus 0.75, axis 180. The minus 2.00 is the sphere, so you are nearsighted by two diopters. The minus 0.75 is the cylinder, the astigmatism correction. The 180 is the axis, the angle that correction sits at. If a box is blank, you do not need it. A plus sphere with an ADD value means distance correction on top and reading help below. To skip the manual read, paste your numbers into our Prescription Decoder for an instant plain-English breakdown and lens recommendations.
The number that is often missing
Many prescriptions leave off PD, your pupillary distance, because the exam does not always record it. You need it to order glasses online, since it centers the lenses over your eyes. You can measure it at home in a mirror. Our PD Ruler tool walks you through it, and how to measure your PD at home covers the method.
What a prescription does not include
A glasses prescription is not a contact lens prescription. Contacts sit on the eye and need a base curve and diameter that glasses do not. A prescription also expires, usually after one to two years, so check the date before you order. It tells the lab your correction, not which frame to pick. For that, start with the Frame Finder.
From our test bench. The mistake we see most is a swapped OD and OS, or a PD left blank. Read left to right, eye by eye, and copy every sign, the minus or the plus, exactly. One dropped minus turns a nearsighted lens into a farsighted one. When a PD is missing, measure it before you order rather than guessing.
FAQ
What do OD and OS mean on a prescription?
OD is your right eye, from the Latin oculus dexter. OS is your left eye, oculus sinister. Some prescriptions use RE and LE instead.
Is a minus number nearsighted or farsighted?
A minus sphere means you are nearsighted and see near objects more clearly. A plus sphere means you are farsighted. The bigger the number, the stronger the correction.
Do I need my PD to order glasses?
Yes. Pupillary distance centers the lenses over your eyes. If it is missing from your prescription, measure it at home before ordering.
Part of Choosing Glasses Frames · Related: how to measure your PD · Browse eyeglasses · Last updated: August 5, 2026
