Eye Test Prescription Explained: How To Read The Numbers

Your eye test prescription reflects the condition of your eyes and the the amount of correction they need. It can help you figure out whether you have myopia, hyperopia or astigmatism — and to what degree.

In this article we’ll explain the numbers and abbreviations that show up in your eye test prescription.


We’ve prepared this table to help you make sense of the abbreviations and numbers that might be on your eye test prescription.

ODShort for the Latin term oculus dexter, which means right eye.
OSShort for the Latin term oculus sinister, which means left eye.
SPHSphere. It indicates how strong the correction needs to be for you to see clearly. A minus () symbol next to this number means you have myopia (also known as nearsightedness). A plus (+) symbol means the prescription is meant to correct farsightedness (hyperopia).
CYLCylinder. It’s the lens power needed to correct astigmatism. If this column is blank, it means you don’t have astigmatism. The cylinder and axis work together to help correct astigmatism.
AxisA number between 1 and 180 degrees. It shows where exactly astigmatism appears in the eye. Will also be blank if you don’t have astigmatism.
PDPupillary Distance. This is the distance between your eyes measured between the pupil center points of each eye.
ADDAdditional lens power. This will be blank unless you have bifocal/progressive lenses. It’s the reading power (“plus” power) for the bottom portion of the lens.
PrismPrismatic power. This is the amount of power needed to correct eye alignment issues that cause double vision. It’s very rare.
BaseThis is the direction of the prism in the lens. Also very rare and is probably blank.

Contact Lenses Prescription

Keep in mind prescriptions for eyeglasses are different than prescriptions for contact lenses. You can only get a contact lens prescription from a contact lens consultation and fitting with an eye care professional.

A contact lens prescription contains additional measurements to accommodate for the unique shape of your eye. Your contact lenses prescription also tells you what brand and type of lens you should get, along with an expiration date.

Eye test prescriptions for contact lenses have to be updated more often to reflect changes in your vision and to ensure they fit correctly.

How Often Should You Get An Eye Test?

As far as how often you should get an eye test, if you don’t have any serious medical issues that affect your vision, you should have a comprehensive eye test every one to two years.

Conclusion — Eye Test Prescription Explained

In this article, we went over how to read an eye test prescription.

Your eye test prescription allows the eyeglass manufacturer to know what type of lenses you need and how strong they need to be. It also shows the degree of nearsightedness, farsightedness, or astigmatism in each of your eyes.

It’s important to go to the eye doctor at least every couple of years to ensure your vision health is good.

If you have any questions don’t hesitate to leave them in the comments below!

Hugo Moreira

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My passion for promoting eye health in communities around the world fuels me to create content that is factually reviewed not only by the most up-to-date scientific research but also by everyday expertise from my personal experience with being nearsighted since I was a child.