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OD stands for "oculus dexter" which is Latin for "right eye".

They mean the same thing: the strength of your prescription. If you're nearsighted you will have a minus (-) before your values, and if you're or farsighted you will have a plus (+).

This is only for people with astigmatism. The axis is a number between 0 and 180 and determines the orientation of the Cylinder (CYL).

OS stands for "oculus sinister" which is Latin for "left eye"

This is for people with astigmatism. This is when one part of the eye needs more correction than the rest. The Cylinder value is written with a minus (-) sign.