CYL and AXIS: Understanding Astigmatism on Your Prescription
If your prescription has numbers under CYL and AXIS, you have astigmatism. It is very common and glasses correct it easily.
What astigmatism is
The front of the eye is not perfectly round, so light focuses unevenly. Things can look slightly blurry or stretched at any distance.
CYL (cylinder)
The amount of astigmatism, in diopters. It can be written with a minus or a plus sign depending on the doctor; both are correct.
AXIS
A number from 1 to 180 that tells the lab the angle of the correction. It has no unit and no sign. AXIS only exists when there is a CYL value.
Type them exactly
When ordering online, copy CYL and AXIS exactly as written for each eye. A wrong axis can make your glasses feel uncomfortable.
Frequently asked questions
Is astigmatism serious?
Usually not. It is a common refractive error that glasses or contact lenses correct.
Why does my CYL have a plus sign?
Some doctors write it in plus form. The lab converts it; just copy it exactly.
Related guides
This guide is for information only and does not replace an eye exam. If you have eye pain, sudden vision loss or flashes of light, see a doctor right away.