About Your Prescription (Rx)

• Your prescription provides the doctor's recommendations for clear and comfortable vision. If you don't know how to read your prescription, this guide will help explain it.

In your prescription, you will see some abbreviations and numbers. Let's go through them to understand what they mean.

OD or O.D is the abbreviation for the Latin term oculus dexter, which means right eye.

OS or O.S is the abbreviation for the Latin term oculus sinister, which means left eye.

SPH or Sphere indicates the lens power needed to correct your vision. A negative sign (-) before the number means you are nearsighted, while a positive sign (+) means you are farsighted. For example, if you see -375, it means -3.75. Sometimes doctors may omit the decimal point, which is common.

CYL or Cylinder indicates the lens power needed to correct astigmatism. If you don't have astigmatism or it is very mild, this section will be blank.

AXIS or AX (X) indicates the curvature of the cornea. The number in this section refers to the angle (from 1 to 180 degrees). If your prescription includes a Cylinder, it must also include AXIS.

PD or Pupillary Distance indicates the distance between the centers of your pupils, measured in millimeters (mm). This value ensures that the center of the lenses is positioned correctly.
If your PD has two numbers (e.g., 29/31), it means the distance from each pupil to the bridge of your nose. The first number always represents the right eye, and the second represents the left eye.

ADD or NV, sometimes indicated as PAL, represents the additional correction you might need for reading or viewing objects up close. This is typically used for progressive or multifocal lenses, and it refers to the additional magnification in the lower part of the lens for multifocal lenses.

Prism: Some people experience double vision because their eyes cannot focus on the same point. Adding a prism shape to the lenses can bend the light entering the eyes, allowing the light seen by each eye to align, thereby eliminating the double image perceived by the brain.

The prism prescription is indicated by Prism or (Δ) and Base.

Base or Base Direction indicates the direction the prism should tilt.

• BU is the abbreviation for Base Up, indicating the direction is upward.
• BD is the abbreviation for Base Down, indicating the direction is downward.
• BI is the abbreviation for Base In, indicating the direction is inward.
• BO is the abbreviation for Base Out, indicating the direction is outward.