Reading Your Eyeglasses Prescription: What Do All Of Those Numbers Mean?

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Vision after Forty

Hello. My name is Lori Frank. I’m fifty-two years old. I had perfect vision until I turned forty-one years of age. It’s funny; you often hear how one's vision starts to change at forty. Well, I can tell you that statement sure has held true for not only me but friends and family too. I never worried about going for yearly eye exams until I noticed that it was getting harder to read road signs when driving. I got my first pair of glasses when I was forty-one, and I’ve been averaging a new prescription at least every other year since. I want to share some of my experiences when it comes to eye exams. I was frightened and wanted to put it off, but there’s really nothing to be afraid of. Moreover, to make things better, eyeglasses are a trend these days!

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Reading Your Eyeglasses Prescription: What Do All Of Those Numbers Mean?

3 February 2016
 Categories: , Blog

After you have an eye exam, your optometrist will give you your prescription for eyeglasses. If the optometrist's office is part of a store that sells eyeglasses, you might not think much about the prescription; you simply hand it to another employee and allow him or her to help you choose frames. If you are ordering your glasses elsewhere, however, you might wonder what all of those numbers mean.

OD and OS

You're going to need to learn a bit of Latin if you want to be able to read your eyeglasses prescription. Luckily, this is a pretty simple lesson: OD stands for "oculus dexter," which means "right eye." OS stands for "oculus sinister," which mean, as you might have guessed, "left eye."

Sphere (SPH)

If you are nearsighted (which means it's difficult for you to see things that are far away), your sphere measurement will be a negative number. If you're farsighted, it will be a positive number. The number itself indicates the curve of the glass or plastic that is necessary to correct your vision; the farther the number is from 0, the more correction needed. For example, if your OD sphere is -1.25 and your OS sphere is -3.50, you will know that you are nearsighted and that your left eye requires more correction than your right eye.

Cylinder (CYL)

If you have an astigmatism, which is an irregularity in the shape of your cornea, the eye doctor will fill in this block. A larger number indicates a less-round cornea. If the cylinder field is filled in, you'll also have a measurement under the axis field; this tells the optician which direction your irregularity lies, so he or she can place the correction in the right place on your eyeglasses lens.

Prism

If your eyes tend not to work together perfectly, you will have a measurement here. If you have double vision at times or you are straining the muscles of one eye when you try to read or drive, you might need some extra correction in the strained eye. If you have a number in this block, you will also have one in the base field, as this will tell the optician where the prism needs to be in your lens.

ADD

Most people need correction for reading as they get older, so this number might increase as you age. It indicates that you need some additional correction for farsightedness. In many cases, a number here will mean that you are a candidate for bifocals.

While reading your eyeglasses prescription might seem complicated, once you know what everything means, it's fairly simple. Talk to your eye doctor, such as Prescription Glasses store in St Johns, if you have questions about your prescription.