OD and OS
These abbreviations stand for "Oculus Dexter" and "Oculus Sinister" which mean "Right Eye" and "Left Eye" in Latin.
Sphere (SPH)
This measurement indicates the lens power necessary for each eye. For nearsightedness, a (+) is used, and for farsightedness a (-) is used. The measurement is in diopters (D).
Cylinder (CYL)
This lens power is used to correct astigmatism. This is also measured in diopters (D). Astigmatism is a common condition where the Cornea or lens of the eye is irregularly shaped....
Axis (Ax)
This measurement is only present if you have astigmatism. The numbers under this column refer to angle degrees (1 to 180) and not diopters (D). If your prescription included Cylinder...
ADD
This measurement is only used for multifocal (progressive or bifocal) lenses. It refers to the added magnifying power that's applied to the bottom part of the lens in multifocal lenses....
Prism
This is the prismatic power used to correct double vision or vision displacement. This happens when your eyes do not align correctly, so it creates two images instead of one, which...
Base
This is the way the base of the prism is facing to correct your vision. This is usually written out as BU (Base Up), BD (Base Down), BI (Base In), or BO (Base Out).
Pupillary Distance (PD)
This measurement is essential to ordering glasses, especially online. This is the distance between the centers of your pupils.