Guide
How to read your prescription
What SPH, CYL, AXIS, ADD and PD mean on an eye prescription, explained simply before you order glasses online.
The short version
Your prescription lists the lens power for each eye. OD is the right eye and OS is the left eye.
What each value means
- SPH (sphere): the main power. A minus sign means short-sighted, a plus sign means long-sighted.
- CYL (cylinder) and AXIS: correct astigmatism. They always go together.
- ADD: extra power for reading, used in progressive and reading lenses.
- PD (pupil distance): the distance between your pupils in millimetres, used to centre the lenses.
Missing a value?
If your prescription has no PD, send it later or message us on WhatsApp and our opticians will help.