Terminology on Eyeglasses Prescriptions

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Terminology on Eyeglasses Prescriptions

Glossary of Eyeglasses Prescriptions Terms

Learning the following terms will help you to understand your eyeglasses prescription and fill out the order form when purchasing your new glasses from Optical Lens Lab.

OD (Right) & OS (Left)

Your prescription will likely use abbreviations for Latin words to indicate left and right eyes. OD is short for oculus dexter, meaning right eye, and OS is short for oculus sinister, meaning left eye. Some eye doctors prefer to modernize their prescriptions, using the abbreviations RE and LE for right eye and left eye.

Pupillary Distance (PD)

Pupillary distance, also called PD, is the distance between the centers of your pupils, measured in millimeters, and is used to align the optical center of your lenses to each pupil.

Your eye doctor might show your PD on your prescription as a single number, as two numbers (dual), or not indicate it at all. If your prescription doesn’t have the PD listed, learn how to measure your PD.

Plano
If there is no prescription in the sphere part of a prescription, eye doctors call that plano (abbreviated as PL). Plano is the zero point between the positive and negative numbers that indicate the strength of a prescription.
Sphere
Sphere, also shown as SPH, shows the strength of your prescription.
Cylinder
Cylinder, abbreviated as CYL, is a measure of lens power shown on your prescription if you have astigmatism. If CYL isn’t indicated on your prescription, either you do not have astigmatism or your astigmatism is mild enough to not need correction.
Axis
Axis is used in conjunction with the cylinder measurement to determine where the cylindrical power should be positioned in your lens. Axis is an angle, expressed as a number between 1 and 180, with 90 as the vertical midpoint and 180 as the horizontal midpoint of the eye. Your eye doctor might write an “x” before the axis number on your prescription.
ADD
ADD is the added magnifying power applied to the bottom part of bifocals or progressive lenses. This additional magnification will help you see small print more clearly. ADD numbers range from .75 to 3.25.
Prism
Prism refers to the prismatic power that is used to correct problems such as double vision. If your prescription lists prism correction, please contact us by phone or email to see if your correction is available.

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