How to Read an Eyeglass Prescription. Knowing how to read an eyeglass prescription could save you money and time when trying to purchase new lenses, especially if you're going to a new doctor or ordering online. To learn what your prescription means and how to read it, follow a few simple steps.
Take note of the numbers your doctor is writing down during your eye exam. Ask questions and ask what each measurement refers to. This will give you a better understanding of the numbers on your prescription.
Ask your doctor for a copy of the prescription and ask to again go over what each of the numbers mean. Most prescription lens websites will offer a guide to help you understand the numbers as well.
Look at the prescription. The OS means your left eye and the OD means your right eye. There will be a plus or minus sign in front of the numbers. A plus sign means you're farsighted and a minus sign means you're nearsighted. The higher the numbers, the more your vision needs correction.
Check to see if you have an astigmatism. If you do, your prescription will look like this: S x C x Axis, where the S is the sphere (the negative or positive number used to determine the degree of nearsighted or farsightedness), C is the cylinder (the negative or positive number used to measure the focusing power of your lens), and Axis refers to the amount of curvature in the lens from 0 to 180 degrees. Your prescription should look something like this: -2.75 +1.00 x 45.
Order your glasses by reading the different elements of the prescription. Make a follow-up appointment after you receive the lenses to make sure they work for you.