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How to Read Your Prescription

December 29, 2020

If you are confused when you got your prescription at hand, but could not figure the meanings of these specification numbers. Don’t worry, We are with you. This article is going to be separated in 3 parts.

Part 1: Samples of Prescription, Check Which one is yours? 
Part 2: Explain some glossaries. 
Part 3: How to select the glasses according to your prescription

Okay. Let’s dive into Part 1 now. 


Part 1: Samples of Prescription. Which one is yours?




The most common prescription format, with values entered with computer and clearly indicates numbers for OD, OS, SPH, CYL. Remarks should be handwritten by doctor.

Sphere (SPH) and Cylinder (CYL) have both (+) or (-) sign. Sphere indicates the lens power needed to correct nearsightedness or farsightedness, in diopters. A plus (+) sign means farsightedness and (-) minus sign means (nearsightedness.

Cylinder power indicates lens power for astigmatism you need. If there is nothing in Cylinder column, that means you do not have or have little astigmatism to correct. Minus sign means nearsighted astigmatism and plus sign means farsighted astigmatism.

Cylinder must follow with Axis value. Axis is defined with a number from 1 to 180. The number 90 corresponds to the vertical merdian of the eye and the number 180 corresponds to the horizontal meridian.



Progressive / Bifocal


Pupillary distance measures the distance between the centers of your pupils. It can be written in different ways, e.g. 63 (Single PD), 32/31 (Dual PD), or 62/60 (Distance PD / Near PD) 

For bifocal or progressive lenses, there will be ADD or NV value needed. The “ADD” value always comes with plus (+) sign. Bifocal or progressive lens glasses must be noted on a prescription, DV means distance vision for nearsightedness, NV means 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.



Common Rx Acronyms

  • OD, Short for Oculus Dexter, refers to right eye.
  • OS, short for Oculus Sinister refers to left eye.
  • OU: short for Oculus Uterque, refers each eye.
  • SPH, short for Sphere, - indicates nearsighted or + indicates farsighted vision.
  • CYL, short for Cylinder, must have Axis value, means lens power for astigmatism
  • PD, Pupillary Distance is the measurement of distance between the pupils.