How to Read Your Eye Prescription

If you've ever stared at your own prescription and felt like you were reading another language, you're not alone.

Here's how to read your eye prescription in plain English: OD and OS for your right and left eye, SPH, CYL, Axis, Add, and sometimes PD and Prism, each with one specific job.

Once you know what each field does, the rows of letters and plus and minus signs stop looking like a mystery and start making sense.

That confidence matters beyond the appointment. It's exactly what you need before choosing your next frame.

Clear terms help you and your provider stay on the same page. That matters whether you're picking a completely different style or reordering an old favorite.

We'll walk through how to read your eye prescription, one line at a time, so you can order your next pair of prescription eyeglasses or matching sunglasses with confidence.

One note before we start. This guide is for understanding the terms on your prescription, not for changing them.

Never adjust or transpose your own numbers. That step belongs to your prescribing provider or lab, not to you.

What Your Prescription Actually Tells You

Your prescribing provider writes a prescription after checking exactly how light bends as it enters each eye.

These prescription terms sound technical, but each one has a specific job. Together they describe how much your lenses need to correct, which eye needs what, and whether astigmatism is part of the picture alongside nearsightedness or farsightedness.

Most prescriptions follow a similar layout, which is why once you learn one, most others start to look familiar. Below, we'll break down each column using a fictional example, so nothing on the page feels like a mystery.

Here's the fictional example we'll use throughout this guide. It belongs to no real patient: OD −2.25 −0.75 x 110, OS −2.00 −0.50 x 085, Add +1.50.

OD and OS: Telling Your Right Eye From Your Left Eye

Your results split into two rows, one for each side, and they're labeled with Latin abbreviations instead of plain English.

O.D. stands for oculus dexter, your right eye. O.S. is short for oculus sinister, the Latin term for your left eye.

Some prescriptions swap the Latin for "RE" and "LE," or use plain English labels instead. The layout varies a little by practice, so check the printed labels on your own paperwork rather than assuming the order.

This distinction still matters. In our fictional example, the two rows carry different readings on purpose, since most people's two eyes don't match exactly.

Your eyeglass prescription is typically presented as a small grid, with the OD row and OS row down one side, and columns for sphere, cylinder, axis, and add power across the top. Some versions add an extra column at the far right for the smaller number of people who need it.

Here's how the fields line up so you can see the pattern at a glance, using our fictional example.

Small layout differences exist between practices and lens labs, so if anything on your own paperwork doesn't match what's above, ask your prescribing provider to walk through it with you.

Sphere (SPH): The Reading Behind Nearsighted or Farsighted

The SPH column tells your lens lab the base power your prescription needs, whether that's for distance, near vision, or both depending on the type of prescription you have.

You'll see a minus sign (−) next to the number if you're nearsighted, which often makes distant objects look blurry. A number means nearsightedness only when it carries that minus sign; a plus sign generally means you're farsighted, and while close-up tasks are often more affected, farsightedness can blur distance vision too depending on its degree.

Sphere is measured in diopters. In our fictional example, one side reads −2.25 and the other reads −2.00, which are simply two individual readings, not a scorecard of whose vision is "worse."

A blank or zero SPH field does not automatically mean no correction is needed anywhere on that prescription. The CYL, Axis, or Add fields can still apply, so read the whole row rather than one column alone.

Cylinder (CYL) and Axis: Reading Astigmatism Correction

If your prescribing provider found astigmatism, you'll see two extra fields next to your sphere reading: CYL and Axis.

Astigmatism happens when your cornea is shaped more like a football than a basketball, so light focuses unevenly instead of landing on one clear point. According to the American Optometric Association, it's a common vision condition that a comprehensive examination can diagnose.

The CYL field shows how much astigmatism correction gets built into the lens, and it's paired with an Axis value between 1 and 180 degrees. Axis describes the orientation of that value, not how mild or severe the underlying issue is.

A CYL value farther from zero means more cylinder power is being built in; it isn't a severity score you can compare across different people. In our fictional example, the right side carries −0.75 x 110, meaning a cylinder value of −0.75 set at an axis of 110 degrees.

A blank CYL and Axis field simply means no cylinder value was specified for that eye. Only your prescribing provider can tell you what that does or doesn't mean for your own eyes.

Add Power and Prism, Explained

Add power shows up for some people who need extra help focusing up close, layered on top of their regular numbers.

Needing an Add value becomes more common as people move through their 40s and beyond, though it isn't automatic for everyone in that age range. This is the field behind progressive lenses, bifocal lenses, and dedicated readers.

It's always a plus value, and it gets layered onto your base prescription rather than replacing it. In our fictional example, the +1.50 Add would apply to both eyes for close-up tasks like reading.

Some prescriptions include a specific, individually prescribed adjustment for certain eye alignment issues. Your prescribing provider is the one who decides whether prism correction fits your particular case, and it isn't a guaranteed fix for every instance of double vision.

Most people will never see this value on their own paperwork. When it does appear, you'll usually see a direction next to it, like "base up" or "base in," which tells the lab how to angle it.

Pupillary Distance and Why It Sits on a Separate Line

Your prescription sometimes lists one more value that isn't part of that sphere-and-cylinder layout at all: pupillary distance, or PD.

PD measures the space between the centers of your pupils, and it tells your optician where to center each lens in front of your eye. Distance PD and near PD are not the same figure, and using the wrong one can leave your finished glasses slightly off-center.

We cover the full details, including how those two numbers differ, in our guide to what PD is and why it matters for glasses.

If your prescribing provider didn't include this figure on your written prescription, you can measure it yourself at home using a phone-based tool before you order. Stronger or complex prescriptions and progressives can also need additional fitting measurements, so ask a qualified fitter to confirm the requirements rather than relying on PD alone.

Eyeglass Prescription vs. Contact Prescription

Here's something that surprises a lot of people: your glasses prescription and your contact prescription are not interchangeable, even if both came from the same visit.

• Eyeglass prescription fields: SPH, CYL, Axis, Add, and PD

• Contact lens prescription fields: those same base values, plus fit-specific measurements like base curve, diameter, and lens brand or material

A contact fit includes measurements specific to your contacts, like base curve and diameter, because the lens sits directly on your eye rather than a few millimeters in front of it. Your prescribing provider also needs to confirm that fit works before finalizing it.

If you wear both, expect two separate sets of paperwork from your visit, not one shared set of readings.

When to Get a New Eye Exam

Prescriptions don't stay current forever, and many providers recommend a new eye exam every one to two years, though your own schedule depends on your age and eye health.

Blurry vision, new headaches, or squinting at things that used to look clear are all reasons to check in with your provider sooner. An outdated prescription doesn't just mean fuzzier vision.

It also means your glasses may no longer match what your eyes actually need. Once you have fresh readings in hand, you're ready to shop with confidence, whether that's your next everyday frame or a dedicated pair of single vision glasses.

Fresh readings also open up more options. Once your provider confirms exactly what you need, you're free to explore new frame shapes and colors instead of sticking with whatever fit last time.

That's a good moment to browse styles you haven't tried, rather than defaulting to the same shape out of habit.

A few habits are worth avoiding along the way:

• Don't assume an older prescription is still current. Many stay valid for a while, but confirm the expiration date with your prescribing provider before reordering.

• Don't guess at a faded or smudged number. Call your provider's office and ask them to confirm it instead of filling one in yourself.

• Don't swap your eyeglasses readings for your contact readings, or the other way around. They come from different measurements and aren't built to be mixed.

• Don't transpose or change your own numbers. Your prescribing provider or lab may need to convert values as part of filling your order, but that step is theirs to handle, not yours.

For a deeper technical breakdown straight from an eye care authority, the American Academy of Ophthalmology also publishes a plain-language explainer, and our Vicci Eyewear concierge team can help if you have questions while you shop.

Once these terms feel familiar, ordering online feels a lot less intimidating. You'll know exactly what each field means the next time you glance at your own paperwork, whether you're shopping for new glasses or getting ready for your next appointment.

Frequently Asked Questions

What do OD and OS mean on my prescription?

OD stands for oculus dexter, your right eye, and OS stands for oculus sinister, your left eye. Some prescriptions use "RE" and "LE" instead of the Latin abbreviations. Always check the printed labels on your own paperwork rather than assuming which row comes first, since layout can vary by practice.

What does a minus sign in front of my SPH number mean?

A minus sign generally means you're nearsighted, so distant objects often look blurry. A plus sign generally means you're farsighted, with close-up tasks usually more affected, though distance vision can be affected too depending on the degree. The exact number reflects the strength of that correction.

Why does my prescription have a CYL and Axis number?

Those two fields appear when your provider found astigmatism that needs correcting. CYL shows how much astigmatism correction gets built into the lens, and Axis shows the orientation of that value, in degrees, rather than how severe the underlying astigmatism is. Both numbers work together on your prescription.

Is my glasses prescription the same as my contact lens prescription?

No. Contact prescriptions include extra measurements like base curve and diameter that don't apply to eyeglasses, since contacts sit directly on your eye instead of a few millimeters in front of it.

You'll typically get two separate sets of paperwork if you wear both, not one shared prescription.

How often should I get a new eye exam?

Many providers recommend a checkup every one to two years, though yours may suggest a different schedule based on your age and eye health. Blurry vision, new headaches, or eye strain are all good reasons to schedule one sooner rather than waiting for your next routine appointment.

Where does PD fit into my prescription?

PD isn't part of that sphere-and-cylinder layout, but it still matters for how your glasses fit and perform. Distance PD and near PD are not the same figure, and a professional fitting is the safest way to confirm either one, especially for complex or progressive lens prescriptions.