How to read my prescription?

Your eyeglass prescription contains several numbers that may look confusing, but each one plays an important role in ensuring you get the correct lenses. Here’s a breakdown of the main components:

  • OD and OS: OD (Oculus Dexter), refers to your right eye and OS (Oculus Sinister) refers to your left eye.
  • SPH (Sphere): It indicates the strength of the lens needed to correct nearsightedness or farsightedness. A minus sign (-) means you are nearsighted, and a plus sign (+) means you are farsighted.
  • CYL (Cylinder): It measures the lens power needed to correct astigmatism, if you have any. Otherwise, this field will be left blank.
  • D.S. (Diopter Simplex): An eye dr. may write DS on an Rx in the Cylinder (CYL) field if no astigmatism correction is needed.
  • AXIS: The axis number tells you the angle at which the astigmatism correction should be positioned on the lens. It’s measured in degrees from 1 to 180. Unless it's D.S on Cylinder, AXIS will be 0/Null. 
  • ADD (also NV-ADD, Near Vision ADD): This is the additional magnifying power for presbyopia correction on a multifocal Rx, can be used for bifocal or progressive lenses.
  • PD (Pupillary Distance): It refers to the distance between your pupils in millimeters. It is used for manufacturers to ensure the optical center of your lenses aligns with your pupils that you can see well through the glasses.
  • Prism: Prism indicates the amount of prismatic power, measured in diopters, needed to compensate for any alignment problems in your eyes.
  • Base: This column indicates the direction of a prism by noting the relative position of its thickest edge, which will either appear in a column of its own or be included in the prism column. The orientation of the prism will be indicated by ‘BU’ (base up), ‘BD’ (base down), ‘BI’ (base in), or ‘BO (base out).

      If you can’t make sense of your eyeglass prescription, you’re not alone. Click here for How to Read My Prescription Example to help you navigate yours.

If you’re unsure how to interpret your prescription, feel free to contact us for assistance!