How to Read Your Eye Prescription

Reading an eye prescription might seem complicated, but once you understand the terms and numbers, it becomes simple. This guide will walk you through each part of your prescription, explaining what it means for your vision and how to make informed choices for your eyewear.

Understanding Your Eye Prescription

When you receive a prescription from your eye doctor, it’s usually broken down into a series of abbreviations and numbers. Here’s a breakdown:

Od/OS

• OD (Oculus Dexter): Refers to your right eye.
• OS (Oculus Sinister): Refers to your left eye.

SPH

• SPH (Sphere): Indicates the strength of the lens needed to correct your vision.
• A minus sign (-) means you have nearsightedness (myopia), while a plus sign (+) indicates farsightedness (hyperopia).

Cyl

• CYL (Cylinder): Measures the degree of astigmatism, which means your eye is shaped more like a football than a basketball.
• If there is no value, it means you don’t have astigmatism.

axis

• Defines the orientation of the astigmatism correction in degrees (0 to 180).
• This number is only present if CYL is listed.

ADD

• The additional magnification needed for reading or close work, commonly found on bifocal or progressive lenses.
• It’s typically written as a plus number, like +1.50.

PRISM

• A correction for people whose eyes have alignment issues. It’s measured in prism diopters (Δ) and helps to align your eyes properly.

Sample Eye Prescription Explained

Here’s a sample eye prescription and a breakdown of what each part means:

OD: -2.00 SPH / -1.00 CYL x 90
OS: -1.50 SPH / -0.75 CYL x 180
ADD: +2.00

Explanation:

This person is nearsighted in both eyes with astigmatism. The right eye requires more correction than the left. The ADD power indicates they need bifocals or progressives for reading.

Frequently Asked Questions

1. Why are there different values for each eye?

It’s common for your eyes to have different levels of correction.

2. What if my prescription includes “Plano”?

“Plano” means no correction is needed for that eye or part of the lens, equivalent to 0.00.

3. Can my prescription change over time?

Yes, vision can change, so it’s important to have regular eye exams.