How to Read an Eyeglass Prescription

Getting a new eyeglass prescription can be overwhelming, especially if you're not familiar with the numerous numbers and abbreviations used on the prescription.

In this article, we'll break down the different components of an eyeglass prescription so that you'll not only know what your prescription means but also how to use it to purchase your new glasses.

Parts of an Eyeglass Prescription

An eyeglass prescription typically consists of the following parts:

OD and OS

OD stands for "oculus dexter," which is Latin for "right eye." OS stands for "oculus sinister," which is Latin for "left eye." Your prescription will have values for both eyes. The numbers for each eye may not be the same, which is perfectly normal.

Sphere (SPH)

Sphere, abbreviated as "SPH," is the first value listed under each eye. This measures the amount of lens power you need to correct your vision. A minus sign (-) indicates that you're nearsighted, while a plus sign (+) indicates that you're farsighted. The higher the number, the stronger the prescription.

Cylinder (CYL)

The second value listed under each eye is the cylinder, abbreviated as "CYL." This value measures the amount of astigmatism correction required. A cylinder value of zero indicates no astigmatism, while any other number indicates the degree of astigmatism.


The axis is always a number between 0 and 180 degrees and indicates the orientation of the astigmatism correction. The axis is listed under the cylinder value.

Addition (ADD)

If you have a progressive lens prescription, you'll see an "ADD" value indicated on your prescription. This represents the additional power needed to correct for the middle-distance and close-range vision. This value is always a positive number, typically ranging from +0.75 to +3.00.

Putting It All Together

Now that you know the different components of an eyeglass prescription, it's time to put it all together. Here's an example of what a prescription would look like:



-2.25 -1.50 x 75

-1.75 -0.75 x 120


In this example, the right eye needs -2.25 sphere correction, -1.50 cylinder correction, and axis correction at 75 degrees. The left eye needs -1.75 sphere correction, -0.75 cylinder correction, and axis correction at 120 degrees.

What To Do With Your Prescription

Now that you have your prescription, it's time to use it to purchase your new eyeglasses. Shop Eyeglasses

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