Learn To Read Your Eye Prescriptions

After an eye exam, your optometrists would write down your prescriptions in numbers and abbreviations. Sometimes you wonder, what does each of them mean? Here’s a short guide to understand them!

OD, OS and OU

OD is short for Oculus Dexter = Right Eye

OS is short for Oculus Sinister = Left Eye

OU is short for Oculus Uterque = Both Eyes


SPH is short for Sphere. This will determine the amount of lens power you may need to have clear vision. The numbers in this column would be associated with a plus (+) sign for Hyperopia (long sighted) or minus (-) sign for Myopia (short sighted).


CYL is short for Cylinder which represents the amount of lens power needed to correct astigmatism. The number is commonly associated with a minus (-) sign. If the column is left blank, you may have little to no astigmatism.


Axis is measured in degrees that range from 1 to 180. This number is needed to ensure correct positioning of astigmatism. Axis will only appear if there is value in CYL.


ADD is short for addition, which gives a magnifying power to your multifocal lens. These are usually prescribed to people with Presbyopia — difficulty on focusing near objects. The number is associated with a plus (+) sign.


Prism power is to correct eye alignments for people with double vision, also known as Diplopia. As the light travels from the eyeglass to the eyes, a prism would bend the light to align the two images into one. The number indicates the value of the prism needed.


Base is used as a guide on the direction Prism should be angled. The value that would be displayed under this column are either “in”, “out”, “up or “down”.


PD is short for pupillary distance. As its name implies, this is a distance measured in millimeters between the center of each pupil.

We hope you will find this guide useful and learn how to read your eyeglass prescription. If you have any doubts, feel free to drop by any of our nearest branch and our eye care professionals will be happy to help!