​How to Read the Numbers in Your Prescription

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Have you ever wondered what the numbers on your prescription lenses mean? We at Daniel Walters want to make you more knowledgeable about eyeglasses by helping you read the numbers in your prescription sheet. In this article, we are going to interpret what all these abbreviated letters and figures mean for you to get a full understanding of your vision status.

OD and OS

If you try to look at your prescription, you will see the letters OD an OS quite a lot. What do these codes stand for, you ask? OD and OS are acronyms for the Latin words oculus dexter and oculus sinister. Oculus dexter refers to the right eye while oculus sinister refers to the left eye. Some clinics have decided to replace OD and OS with RE and LE which seems more straightforward.

Sometimes, you will see the code OU which stands for oculus uterque, meaning both eyes.



SPH is short for the word Sphere. Measured in Diopters (D), the number under SPH shows the amount of lens power prescribed by the eye doctor to correct nearsightedness or farsightedness. Nearsightedness or myopia is when you are more adept to seeing things in a shorter distance while farsightedness or hyperopia is the opposite. A negative sign (-) on your SPH means that you are nearsighted while a positive sign (+) or the absence of the minus sign means that you are farsighted. The severity of your eye problem goes higher as the numbers on your SPH moves away from zero (0).


CYL is short for the word Cylinder. Your CYL basically shows how much power your lenses need to correct astigmatism. Astigmatism is when your eye finds it difficult to focus the light it receives to interpret objects sharply. The number could have a negative sign on it to adjust an eye with nearsighted astigmatism or a positive sign for an eye with farsighted astigmatism. Cylinder power is always in accordance to the sphere power.

A blank space on the CYL section basically means that your eyes are free of astigmatism or they are way too mild to be treated.

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Axis identifies the lens meridian that holds no cylinder power to fix astigmatism. It is measured with numbers from 1 to 180. The number 90 parallels to the vertical meridian of your eye, and the number 180 aligns the horizontal meridian. Accurate lens prescriptions with an indicated cylinder power will always have an accompanying axis value which proceeds after the CYL number and is preceded by the letter “x”.


Add stands for the added magnifying power applied to the lowermost part of multifocal lenses. This is made for lenses prescribed to elder people with presbyopia or farsightedness caused by the natural process of aging. The number for added magnifying power is always going to be positive and it could be stated with or without a plus sign. The number commonly moves in a scale of +0.75 D to +3.00 D for both eyes.

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Prism indicates a number showing the prismatic power to correct eye alignment problems. Not a lot of prescriptions have this but just to let you know, prism is measured in prism diopters or p.d. Prism diopters can also be written in the form of a superscript triangle.


PD stands for Pupillary Distance or the distance between the centers of each pupil. This number will never have to change once you reach the adult age. The pupillary distance number plays a significant role in ensuring accurate lens fitting. The measurement of the proper PD allows the center of the lens to align with the midpoint of the pupil for your visual comfort and function.

Daniel Walters offers everyone stylish eyeglasses with accurate prescription in very affordable prices. Choose from a wide variety of eyeglasses starting from those above and send in your prescription today! 

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