OD and OS
Understanding your prescription begins with knowing what “OD” and “OS” mean. At its most basic level “OD” stands for “Right Eye” and “OS” stands for “Left Eye.”
On a few instances, your prescription will have a label of “UD.” This stands for both eyes.
On your prescription, the information for the right eye (OD) will come before the information for the left eye (OS).
Eyeglass Prescription Terminology:
Sphere indicates the amount of lens power prescribed to correct nearsightedness and farsightedness. If you see a (-) sign, you are nearsighted. If you see a (+) sign, you are farsighted.
Cylinder indicates the amount of lens power for astigmatism. If this column is blank, it means, you have no astigmatism.
The number in the (CYL) column may be preceded with a minus sign(near sighted astigmatism) or plus sign (farsighted astigmatism).
Axis signifies the angle of astigmatism correction and ranges from 1 to 180 degrees.
Add is the added magnifying power applied to the bottom part of multifocal lenses to correct presbyopia.
Prism is the power prescribed to rectify eye alignment issues.