How to Read Your Glasses Prescription (So You Don’t Order the Wrong Lenses)

Ok so you’ve just left the optometrist with a little slip of paper covered in letters and numbers that mean absolutely nothing to you, and now you’re trying to order glasses online and the checkout form wants you to type in “AXIS” like you’re supposed to already know what that is. Fair, honestly, nobody explains this properly at the appointment, they just hand you the paper and send you on your way.

This is genuinely not complicated once someone actually walks you through it, it just looks intimidating because it’s a wall of abbreviations. Five minutes and you’ll be able to read your own prescription properly, which matters, because getting even one of these numbers wrong when ordering online means the wrong lenses land on your doorstep.

The Basic Layout of a Glasses Prescription

Almost every prescription is a small table, two rows, a handful of columns. The rows are your two eyes. OD is your right eye (it’s Latin, oculus dexter, don’t worry about memorising that), OS is your left eye. Sometimes you’ll see OU too, which just means both eyes together. Right eye is always listed first, on the top row.

The columns are where it gets more specific, SPH, CYL, AXIS, sometimes ADD, and PD sitting off to the side on its own. We’ll go through each one.

SPH: How Nearsighted or Farsighted You Are

SPH stands for sphere, and it’s the main number, the one doing most of the work. A minus number means you’re nearsighted (things far away are blurry). A plus number means you’re farsighted (things up close are the problem). The bigger the number, further from zero, the stronger the correction you need. Something like -1.00 is a fairly mild prescription, -6.00 is getting into stronger territory.

CYL and AXIS: Astigmatism, Explained Without the Jargon

These two only show up together, if one’s blank the other should be too. CYL (cylinder) shows up if you have astigmatism, which just means your cornea isn’t perfectly round, more like a rugby ball than a football, and that shape distorts vision at certain angles. CYL tells the lens how much correction to apply for that. AXIS, a number between 1 and 180, tells the lens exactly where on the eye to apply it. Think of CYL as “how much” and AXIS as “where.”

If your prescription has nothing in the CYL box, or it says “DS” or “SPH” there instead of a number, that’s just telling you there’s no astigmatism to correct, totally normal, don’t overthink it.

ADD: Only Relevant If You Need Reading Correction Too

ADD shows up on prescriptions for progressives or bifocals, it’s the extra magnifying power built into the bottom part of the lens for reading and close-up work. Always a positive number, usually somewhere between +0.75 and +3.00. If your prescription doesn’t mention ADD at all, it just means you don’t need that extra correction, single vision lenses will do the job fine.

PD: The One Number People Actually Forget

PD is pupillary distance, the gap in millimetres between the centres of your two pupils. It’s not always printed on the prescription slip itself since it’s more of an optical measurement than a medical one, but you absolutely need it to order glasses online, it’s what tells the lab where to centre the actual optical centre of each lens on your face. Get it wrong and you can end up with mild eye strain even with the right SPH and CYL numbers.

If your optometrist didn’t give you a PD, or you’ve lost the paper, it’s genuinely easy to measure yourself with a ruler and a mirror, or with an online tool. If you’re ordering through us, our PD calculator walks you through it in under a minute.

Putting It All Together: A Quick Example

Say your prescription reads OD: SPH -2.00, CYL -0.75, AXIS 90, and OS: SPH -1.75, CYL -0.50, AXIS 85, PD 63. That’s telling you your right eye is more nearsighted than your left, both eyes have a bit of astigmatism (mild, under 1.00), the astigmatism correction needs to sit at almost exactly the vertical angle in both eyes (85 and 90 are close to 90, which is vertical), and your lenses need to be centred 63mm apart. That’s the whole story, once you know what each column means it basically reads itself.

A Few Frames Worth Trying Once You Know Your Numbers

Whatever your prescription looks like, most of our frames handle single vision, bifocal, and progressive lenses without issue, worth double-checking the lens height on anything with a very shallow or narrow shape though, progressives specifically need a bit of vertical room to work properly.

PRAIRIE Titanium IP Plating Rimless Cat-Eye Glasses Frames

Frame type: Rimless (cat-eye) | Material: Titanium IP plating | Weight: 11.2g | Price: $159

Fully customisable lens shape and size since it’s rimless, which is handy if your prescription needs a specific lens height for progressives. Comes with a free diamond cut edge on every order.

See the PRAIRIE frames →

SENO Titanium Rectangle Frames

Frame type: Full rim | Material: Titanium | Weight: 14g (without demo lenses) | Price: $159

A generous 148mm width and a proper full rim build, plenty of lens height for progressive or bifocal ADD corrections without needing to size up. Black, Bronze, or Gold.

See the SENO frames →

ANSA Composite Front and Titanium Temples Glasses

Frame type: Full rim | Material: Composite front, titanium temples | Weight: 9.3g | Price: $149

Progressive-friendly and genuinely unisex, gender-tagged Men, Unisex, and Women on the actual listing. At 9.3 grams it’s barely there, a good option if you want the extra lens height of a full rim build without the usual weight that comes with it.

See the ANSA frames →

How to Read Your Glasses Prescription: FAQ

What does OD and OS mean on a prescription?

OD is your right eye and OS is your left eye, from the Latin terms oculus dexter and oculus sinister. Right eye is always listed on the top row. You’ll occasionally see OU too, meaning both eyes together.

What if my CYL and AXIS boxes are blank?

Totally normal, it just means you don’t have astigmatism to correct. Some prescriptions write “DS” or “SPH” in that spot instead of leaving it empty, same meaning either way.

Can I use my contact lens prescription to order glasses?

No, they’re not interchangeable. Contacts sit directly on your eye while glasses sit a small distance away, so the correction strength needed is actually different between the two, even for the same person.

What if my prescription doesn’t list a PD?

It’s common for PD to be left off since it’s more of a fitting measurement than a medical one. You can measure it yourself with a ruler and mirror, or use an online PD calculator, ours takes under a minute.

How often should I actually update this prescription?

Prescriptions do drift over time, so it’s not a “get it once and forget it” document. Worth checking in with your eye doctor regularly rather than assuming last year’s numbers still apply.

A Quick Word on Getting the Lenses Right

Once you can actually read your own prescription, ordering online stops being a guessing game. Want to double check yourself against a tool instead of just this article, our Prescription Decoder walks through SPH, CYL, and AXIS interactively. If you’re weighing up lens options too, our guides on the benefits of high index lenses and the difference between high index and regular lenses are worth a read, especially if your SPH number is on the stronger side. And if it’s just been a while since your last exam, our piece on how often you should replace your prescription glasses covers that too. For a more clinical breakdown of everything covered here, Versant Health’s guide to reading your eyeglass prescription is a solid reference.