Your eyeglass prescription looks like a math test you forgot to study for, but it is actually a straightforward map of what your eyes need. Once you know what each abbreviation means, the whole thing makes sense. Here is the quick translation.
OD (oculus dexter) is your right eye, and OS (oculus sinister) is your left. Some prescriptions modernize this to RE and LE. If you ever see OU, that simply means both eyes together. No, your doctor is not being sinister — it is just Latin.
Sphere (SPH) is the main strength of your lens. A minus sign means you are nearsighted (distance is blurry); a plus sign means you are farsighted. Cylinder (CYL) and axis appear when you have astigmatism, a very common and very correctable difference in the curve of your eye. Cylinder is the amount of correction, and axis (a number from 1 to 180) tells the lab which direction to orient it.
If you see “ADD,” that is the extra magnifying power for reading, found on bifocal or progressive prescriptions. And “PD,” or pupillary distance, is the space between your pupils — used to center your lenses correctly.
Your glasses prescription is not the same as a contact lens prescription. Contacts sit directly on the eye, so they require additional measurements and a fitting. If you would like both, we will sort that out at your exam. Bring any questions to your visit — decoding prescriptions is one of our favorite party tricks.
PD is your pupillary distance — the distance between your pupils. It ensures the optical center of each lens lines up with your eye, which keeps your vision sharp and comfortable.
No. Contacts need their own measurements and a fitting. A glasses prescription alone does not contain the information required to order lenses safely.
Medically reviewed by Dr. Jason Siegmund, OD, a board-certified optometric physician at Siegmund Eye Care in Myrtle Beach.
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