Glasses Prescription

How to Read a Glasses Prescription

OD vs. OS Eye

OD is short for the Latin term oculus dexter which means right eye.
OS is an abbreviation of the Latin oculus sinister which means left eye.


The sphere (SPH) on your prescription indicates the lens power you need to see clearly. A minus (-) symbol next to this number means you’re nearsighted, and a plus (+) symbol means the prescription is meant to correct farsightedness.
A nearsighted prescription will feature a number with a minus (-) symbol in the ‘sphere’ box. This means your lenses will be shaped to improve your distance vision. A prescription for someone who is farsighted will feature a number with a plus (+) symbol in the ‘sphere’ box. This indicates that your lens should be shaped to correct near vision.


The cylinder (CYL) number indicates the lens power needed to correct astigmatism. If this column is blank, it means you don’t have an astigmatism.
If you have an astigmatism, you will have a number in the ‘cylinder’ column of your prescription that indicates the lens power needed to correct the astigmatism. There will also be a number in the ‘axis’ column that’s needed for astigmatism correction.


An axis number will also be included if you have an astigmatism. This number shows the angle of the lens that shouldn’t feature a cylinder power to correct your astigmatism.


A multifocal prescription will include an ADD value, sometimes marked as NV. This indicates the required strength for the near prescription in your lens.

Astigmatism severity scale:

CYL indicates the severity of your astigmatism in diopters.
Axis value indicates where your astigmatism is positioned in degrees, ranging from 0 to 180.

Sacle CYL Value
Mild less than 1.00 diopter
Moderate 1.00 to 2.00 diopters
Severe 2.00 to 3.00 diopters
Extreme >3.00