How to Read Your Prescription

If you can’t make sense of your eyeglass prescription, you’re not alone.

Common Rx Acronyms

  • OD=Oculus Dexter refers to right eye.
  • OS=Oculus Sinister refers to left eye.
  • SPH=Sphere corrects nearsighted or farsighted vision.
  • CYL=Cylinder combined with Axis corrects astigmatism.
  • PD=Pupillary Distance is the measurement of distance between the pupils.

Here are some common prescription types to help you navigate yours.

Standard Grid Format

This is the most common format with clearly printed fields for OD, OS, SPH, CYL, etc.; values are usually entered with computer, but may be handwritten by doctor.

Rx Notes:

Sphere (SPH) and Cylinder (CYL) always have a (+) or (-) sign.

On any prescription, PD can be written in different ways: e.g., 62 (Single PD), 33/31 (Dual PD), or 62/60 (Distance PD/Near PD).

Standard RX

Blank Format

The information on this free-form prescription is usually handwritten.

blanket RX

Progressive / Bifocal

For multi-focal glasses, as well as reading and computer glasses, your Rx will include an ADD or NV value. This number always has a (+) sign.

Rx Note:

The type of Rx glasses may be noted on a prescription, such as DV [Distance Vision/nearsightedness] and NV [Near Vision/reading].

Prescription with Prism

The less common prism Rx refers to the amount of prismatic power needed to compensate for eye alignment issues (e.g., double vision or “lazy eye”). The prism Rx will have two values: PRISM & BASE.

Rx Note:

BO=Base Out, BI=Base In, BU=Base Up, and BD (or BDn)=Base Down.

Vertical Prescription

Unlike typical Rx formats, with values going from left to right, the vertical Rx values are listed top to bottom. This format is less common in the US.