How to Read Your Eyeglass Prescription: OD, OS, CYL & AXIS Explained

The 60-second version

OD (oculus dexter) is your right eye; OS (oculus sinister) is your left. SPH (sphere) is the main power — a minus number means you're nearsighted, plus means farsighted. CYL (cylinder) and AXIS only appear if you have astigmatism: CYL is the strength of the correction, AXIS (0–180°) is its angle. ADD is extra magnifying power for reading, used in bifocals and progressives. PD is your pupillary distance in millimetres — the one number opticians most often leave off.

What each number means for buying online

For single-vision orders, SPH, CYL and AXIS for each eye plus your PD are everything a lab needs. If your prescription is under two years old and your vision hasn't changed, it's valid to order with.

Higher powers (SPH beyond ±4.00) benefit from high-index lenses — thinner and lighter for the same correction. If your ADD value is filled in, you're a candidate for progressives rather than carrying two pairs.

Don't have your PD? No problem

Most Pakistani prescriptions omit PD. You can measure it with a ruler and a mirror (average adult range: 54–74mm), or simply order at Klarity and send a straight-on selfie holding any standard card under your chin — our opticians calculate PD from the card's known width. Handwritten prescription? Snap a photo and send it on WhatsApp; we'll verify it within hours.