How to Read Your Prescription


Prescriptions are commonly written on a sheet with a grid format. On these grid sheets, the SPH (sphere) is listed first, followed by CYL (cylinder), AXIS, and PRISM. For progressive or bifocal glasses, the prescription will also include and ADD value. These values are separated into two rows, one for O.D. (Oculus Dexter) and O.S. (Oculus Sinister). To the uninformed, these terms can be a cause of major confusion. But don’t worry! We have listed the functions of these terms for you below:

O.D. (Oculus Dexter): right eye

O.S. (Oculus Sinister): left eye

SPH (Sphere): corrects near or far-sightedness.

CYL (Cylinder) and AXIS: combined together, these optical features correct astigmatism, which is an imperfection in the eye’s curvature that causes blurry vision.

PRISM: used to correct diplopia, or double vision.

ADD: added magnifying power on the bottom part of multifocal lenses to correct farsightedness. For more prescription acronyms, click here.