Prescriptions · 5 min read
How to read your eye prescription
SPH, CYL, AXIS, ADD, PD — what every number on your prescription means.
Your prescription looks like a spreadsheet of abbreviations. Here's what each one means.
The key terms
- • OD = right eye, OS = left eye
- • SPH (sphere) = the main power; minus for short-sight, plus for long-sight
- • CYL (cylinder) = astigmatism correction
- • AXIS = the angle of that astigmatism, 0–180
- • ADD = extra reading power (progressives/bifocals)
- • PD = pupillary distance in mm, so lenses centre on your eyes
Don't have your PD?
No problem — we verify it for you, or read it from your current lenses during doorstep delivery.
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