Know Your Prescription Data

by LewisCharlotte on Nov 18, 2021

Know Your Prescription Data

The professional terms on the eyeglasses prescription often confusing. We know it is hard for most people to recognize, but they are very important when it comes to eyeglasses. So it is time to have a better understanding of eyeglasses prescription.



OD is the abbreviation of oculus dexter. It means the right eye.



OS is the abbreviation of oculus sinister. It means the left eye.



Sphere shows the amount of lens power prescribed to correct nearsightedness or farsightedness. If it appears a minus sign(-), it means you are nearsighted. If it appears a plus sign(+), it means you are farsighted. The farther the number away from 0.00, the stronger and thinner then prescription lens required.


Cylinder (CYL):

It indicates the amount of astigmatism caused by an irregularly shaped cornea. You don’ t need to adjust if nothing is appeared in this column. If there is a plus sign(+), you need to correcting your farsighted astigmatism. If there is a minus sign(-), you need to correcting your nearsighted astigmatism.



PD is the short of pupil distance. The distance between the centers of lens should match the pupil distance. Otherwise, you will feel uncomfortable and it affects your vision even if the degree is correct.



it is the direction of the astigmatism, measured in degrees. It shows the angle between the two meridians of an astigmatic eye.



It indicates the magnifying power used to correct presbyopia that happens with age. The number usually range from +0.75 to 3.00.



it stands for the amount of prismatic power which is the compensation for eye alignment problems. And it usually appears decimal or fraction followed by base direction. For example, “BU” refers to “base up”, “BD” refers to “base down”, “BI” refers to “ base in” and “BO” refers to “base out”.


You must know more about eyeglasses prescription after this introduction, just picking up the eyeglasses that is suitable for yourself.


Refractive Index

Refractive index is the number of the lens's ability to refract light.Usually, the higher the refractive index, the thinner the lens. Lens edge thickness is related to selected lens’ refractive index, frame size and pupil distance

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