Woman inserting a contact lens in eye.

How to Read a Contact Lens Prescription

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If you’re a contact lens wearer, you’ve been to an eye doctor and had an eye exam, along with a contact lens fitting and evaluation. After your exam, someone up front usually helps you order your contacts and you leave with a prescription.

Ever wonder what your prescription really means? Below is a picture of a typical prescription and what each item means.

How to read a contact lens prescription explanation


  • OD means right eye. Fun fact: OD stands for “oculus dexter,” which is Latin for “right eye.”
  • OS means left eye. Fun fact: OS stands for “oculus sinister,” which is Latin for “left eye.”


  • This is the power of your distance prescription.


  • This stands for Base Curve. It measures in millimeters the curvature on the inside of the lens to ensure it matches the shape of your eyeball. The number is usually between eight and ten.


  • This stands for diameter. This is the measure of the lens in millimeters from one side to the other, as measured by a straight line passing through the center. This number is very important—if the diameter is too large or small your contact lens will move around on your eye and cause irritation.


  • This is the brand your VSP network doctor is recommending you purchase. In the U.S., your eye doctor will always specify the brand that’s best for your eyes. Not all brands are the same; your doctor will consider materials used, water content, and other factors in determining the brand that’s best suited for your visual needs.

If you have any questions, you can always ask your doctor. You can purchase your contacts at your doctor’s office or if you prefer to shop online, visit Eyeconic.com. If you don’t have vision insurance and need coverage for contact lenses, visit VSPDirect.com to purchase a VSP Individual Vision Plan. Plans cover an annual eye exam, glasses and/or contact lenses, and more.

This is a guest post written by VSP employee Jessica Caswell.


  • What shout a person do if a brand was not recommended by their doctor?

  • I HATE Auto Correct… that was supposed to be SHOULD!

  • I’ve been wanting to purchase some more contacts online, but then I realized that I had no idea what my prescription meant.Thanks so much for explaining that.

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