How to Read Your Contact Lens Prescription

When you receive your contact lens prescription from your eye doctor, it can appear complex and difficult to understand at first glance. However, breaking down the information step-by-step makes it much easier to comprehend and ensures you get the correct lenses for your eyes.


Photo by Ketut Subiyanto

Understanding the Components

  • OD and OS: These abbreviations stand for oculus dexter and oculus sinister, which are Latin terms for right eye (OD) and left eye (OS) respectively.
  • Sphere (SPH): This indicates the lens power prescribed to correct nearsightedness (negative values) or farsightedness (positive values).
  • Cylinder (CYL): If you have astigmatism, this number shows the lens power needed to correct it, preceded by a minus sign. If you see DS or SPH here, this signifies the prescription is for a spherical lens, meaning there is no astigmatism correction.
  • Axis: This specifies the orientation of the cylindrical power to correct astigmatism, measured in degrees from 1 to 180.
  • Addition (ADD): This is used for multifocal lenses to indicate the additional magnifying power applied to the reading area.
  • Base Curve (BC): The curvature of the back surface of the contact lens, measured in millimeters. Your doctor will check the fit of the lens to ensure that it is a good match for your eye.
  • Diameter (DIA): The width of the contact lens in millimeters.
  • Brand: Your doctor will specify a particular brand of contact lenses that they have approved the prescription for.
  • Expiration Date: The contact lens prescription is valid for a specified period of time, typically 1-2 years from the date of your eye exam.

Contact Lens RxTips for Ordering Your Contact Lenses

  • Consult Your Eye Doctor: If you have any questions about your prescription or need clarification, always seek clarification from your eye care professional.
  • Double-Check the Details: Input these values carefully to ensure you receive the correct contact lenses.
  • Understand Additional Terms: Familiarize yourself with terms like “toric” (for astigmatism) or “multifocal” (for presbyopia) if they apply to your prescription.
  • Trial Lenses: Try a sample lens before ordering a supply to ensure comfort and vision. Your eye doctor should be able to provide a trial contact lens from the manufacturer.

contact lens

By familiarizing yourself with the key terms and measurements, you can confidently order the correct contact lenses that provide optimal vision and comfort. If you ever have questions or concerns about your prescription, don’t hesitate to reach out to your eye care provider for assistance.

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Ivan Yong

Dr. Ivan Yong is an optometrist with over 12 years of experience in the optical industry. He earned his doctorate from the Southern California College of Optometry and has practiced in multiple settings, including private practice, community health, and ophthalmology. Dr. Yong aims to expand access to affordable eyewear and improve eye health worldwide.