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Learn how to read your glasses prescription (Rx). When know what the optical terms and abbreviations mean, your prescription is easy to understand.

Glassesgallery lens info image - Prescription information
Glassesgallery lens info image - PD1


  • Distance Vision: Also known as being farsighted, longsighted or hyperopia. Closer objects appear to be blurred.
  • Near Vision: Also known as being nearsighted, shortsighted or myopia. Nearsighted means that with your natural uncorrected vision, you can see close or "near" objects but those further out get blurry.
PD icon


Your PD is the distance between your pupils. PD is used to center lenses correctly over your eyes.
  • Monocular PD: PD measurement written as two numbers e.g. 32/33
  • Binocular PD: PD measurement written as one number (if the left and right side have been added together) e.g. 65
Glassesgallery lens info image - SPH


Sphere indicates the amount of lens power prescribed to correct nearsightedness or farsightedness. If the number has a minus sign (-), you are nearsighted; if the number has a plus sign (+) or there's no plus or a minus sign, you are farsighted.
Glassesgallery lens info image - CYL


Cylinder indicates the amount of lens power for astigmatism. If nothing appears in this column, you have no astigmatism, or yours is so slight that it is not necessary to correct it.
Glassesgallery lens info image - Axis


Axis describes the lens meridian that contains cylinder power to correct astigmatism. The axis is defined with a number from 1 to 180. If your eyeglass prescription includes cylinder power, it also must include an axis value. It comes after the cylinder power and is preceded by an "x" when written freehand.
Glassesgallery lens info - add


Add is the added magnifying power applied to the bottom part of multifocal lenses to correct presbyopia. The number always appears with a plus sign, and even if it doesn't, it's understood as a "plus" power. It usually ranges from +0.75 to +3.00 D and will be the same power for both eyes.
Glassesgallery lens info image - OD

O.D. and O.S.

OD and OS are Latin abbreviations. Oculus means eye, dexter means right and sinistra means left in Latin. OD stands for right eye. OS stands for left eye.
Glassesgallery lens info - prism


Prism is the amount of prismatic power. It's prescribed to compensate for eye alignment problems. It's not commonly found in glasses prescriptions. When present, it is indicated in either metric or fractional English units (0.5 or ½, for example). The direction of the prism is indicated by noting the relative position of its "BASE" or the thickest edge. Four abbreviations are used for prism direction: BU = base up; BD = base down; BI = base in (toward the wearer's nose); BO = base out (toward the wearer's ear).
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