How to Read Your Contact Lens Prescription: A Complete Guide

Introduction

So, you’ve decided to make the switch from glasses to contact lenses. Congratulations! Welcome to the world of clearer vision and a slightly more complicated prescription. Don’t worry, though. Reading your contact lens prescription is simpler than you might think. In this guide, we’ll break it down for you step-by-step, so you can be confident the next time you order your contacts.

Understanding the Terminology

Before we jump into the numbers, let’s go over some of the terms you might see on your contact lens prescription:

OD: Oculus Dexter, or your right eye.

OS: Oculus Sinister, or your left eye.

SPH: Sphere, or the amount of lens power needed to correct your vision. A minus (-) sign indicates nearsightedness, while a plus (+) sign indicates farsightedness.

CYL: Cylinder, or the amount of lens power needed to correct astigmatism. This number will have either a plus (+) or minus (-) sign.

AXIS: The orientation of the cylinder power. This number ranges from 0 to 180 degrees.

BC: Base Curve, or the curvature of the lens surface. This is measured in millimeters (mm).

DIA: Diameter, or the size of the contact lens. This is also measured in millimeters (mm).

Putting it All Together

Now that you know the terminology, let’s look at an example prescription:

OD: -2.50 -0.75 x 180

OS: -3.00 -1.25 x 170

BC: 8.5

DIA: 14.0

Here’s how to read this prescription:

Your right eye (OD) has a sphere power of -2.50, a cylinder power of -0.75, and an axis orientation of 180 degrees.

Your left eye (OS) has a sphere power of -3.00, a cylinder power of -1.25, and an axis orientation of 170 degrees.

Both eyes have a base curve (BC) of 8.5 mm and a diameter (DIA) of 14.0 mm.

Takeaway

Reading your contact lens prescription might seem intimidating at first, but with a little bit of knowledge, it’s easy to understand. Knowing how to read your prescription ensures that you’re ordering the right contacts for your eyes, which means clearer vision and happier eyes. Happy ordering!