READ YOUR PRESCRIPTION

OD, OS, sphere, cylinder, axis, ADD — the numbers on the card, decoded in plain English.

Your prescription looks like a secret code, but it's just six measurements and a Latin hangover. OD is your right eye (oculus dexter), OS is your left (oculus sinister). Everything else is a column under one of those two headings. Once you know what each row means, you'll never feel blind at the optical counter again.

Sphere (SPH) is the main event: the lens power that corrects nearsightedness or farsightedness, measured in diopters. Minus numbers mean nearsighted — you see close, not far. Plus numbers mean farsighted. The bigger the number, the stronger the correction, and the more your lens material choice matters. A -1.50 can wear almost anything; a -8.00 needs high-index and a smart frame choice. Cylinder (CYL) and Axis together describe astigmatism — an irregular curve in your eye that blurs vision at certain angles. Cylinder is the amount of correction; axis, a number from 1 to 180, is the orientation. If those columns are blank, you don't have astigmatism. Lucky you.

ADD is the addition: extra magnifying power for close-up work, and it only appears if you're presbyopic — generally 40-plus. It's what turns a single-vision prescription into progressives or bifocals. Then there's PD, pupillary distance, sometimes on a separate measurement: the millimeter distance between your pupils, which centers the optics on your eyes. Get it wrong and even a perfect prescription feels off. Finally, prism is rare — a correction for eye alignment issues that most prescriptions never include.

Practical takeaway: the sphere tells you how strong, the cylinder and axis tell you how complex, and the ADD tells you whether you're in progressive territory. Keep a photo of your prescription on your phone. It's yours. *Talk to your eye doctor if any number on your card confuses you — that's literally their job.*

"Minus is nearsighted, plus is farsighted, and PD is the number everyone forgets."