How to Read and Understand Your Eyeglass Prescription (The Easy Way)

Learn how to read and understand your eyeglass prescription easily. Clear guide to SPH, CYL, AXIS, and PD for accurate online orders.

If you’ve ever looked at your eyeglass prescription and thought, “What does all of this even mean?” - you’re not alone.
Those small abbreviations and numbers can feel confusing, but once you understand the basics, reading your prescription becomes surprisingly simple.

In this guide, we’ll break everything down in a clear and practical way.

What Is an Eyeglass Prescription?

An eyeglass prescription is a set of measurements that define how your lenses should be made to correct your vision.

It usually includes values for:

- Nearsightedness or farsightedness
- Astigmatism
- Lens alignment

Common Abbreviations You’ll See

Here are the key terms you’ll find on most prescriptions:

SPH (Sphere)

This number shows the strength of your lens.

- Minus (-) → nearsightedness (you see close objects clearly, distant ones blurry)
- Plus (+) → farsightedness (you see distant objects clearly, close ones blurry)

CYL (Cylinder)

This value indicates astigmatism, meaning your eye doesn’t focus light evenly.

Not everyone has this - if it’s blank, you don’t have astigmatism.

AXIS

Axis works together with CYL and shows the direction of astigmatism.

It’s measured from 0 to 180 degrees.

PD (Pupillary Distance)

This is the distance between your pupils.

It’s essential for properly centering your lenses - especially important for online orders.

Example Prescription (Simple Breakdown)

Let’s say your prescription looks like this:

- Right Eye (OD): -2.00 SPH / -0.50 CYL / 90 AXIS
- Left Eye (OS): -1.75 SPH

This means:

- You are nearsighted in both eyes
- You have slight astigmatism in your right eye
- Your lenses need to be precisely aligned for clear vision

OD and OS - What Do They Mean?

- OD (Oculus Dexter) → Right eye
- OS (Oculus Sinister) → Left eye

Sometimes you’ll also see:

- OU → Both eyes

Why Understanding Your Prescription Matters

Knowing how to read your prescription helps you:

- Order glasses online with confidence
- Understand your vision changes
- Communicate better with your optician
- Avoid input mistakes when ordering lenses