OD = right eye
OS = left eye
OU = both eyes
SPH = sphere; lens power for nearsightedness or farsightedness
Minus sign (-) = nearsightedness
Plus sign (+) = farsightedness
CYL = cylinder; amount of astigmatism correction
AXIS = direction of astigmatism correction, from 1 to 180
ADD = additional magnifying power for reading or bifocals/progressives
Prism = lens shift used to correct eye alignment
Base = direction of prism
PD = pupillary distance; distance between pupils
Example: -2.00 SPH = 2 diopters of nearsighted correction
Example: +1.50 SPH = 1.5 diopters of farsighted correction
Example: -1.00 CYL x 90 = astigmatism correction at axis 90
Example: ADD +2.00 = extra near-vision power
If CYL and AXIS are listed, astigmatism is being corrected
If only SPH is listed, there is no astigmatism correction
Higher absolute numbers mean stronger lens power
Prescription values are usually measured in diopters
Some prescriptions include separate values for each eye
Some prescriptions include distance and near sections
Some prescriptions include prism values in fractions or decimals