How to read an eyeglass prescription
The lens power of eyeglasses is measured in diopters. This measurement reflects the amount of power necessary to focus images directly on to the retina. When looking at an eyeglasses prescription, you will see the following abbreviations:
| O.D. - Oculus dextral simply refers to the right eye (sometimes the abbreviation RE is used). | O.S. - Oculus sinister refers to the left eye (sometimes the abbreviation LE is used). |
In addition, the eyeglass prescription may also contain the following measurements.
| Sphere |
This number measurement reflects the extent of the nearsightedness or farsightedness. |
|
Cylinder |
This number measurement refers to the amount of astigmatism (an irregularly shaped cornea which causes blurring) in the eye. |
|
Axis |
This number measurement describes the astigmatism in degrees from the horizontal (most left and right eyes have the same axis in astigmatism) axis. |
Bifocal prescriptions, which correct both nearsightedness and farsightedness, usually have an additional measurement listed on the prescription as “add,” to indicate the strength of the lens.
Did You Know?
By federal law, an eye doctor is required to provide an eyeglass prescription, following an eye exam, at no extra cost. In addition, under federal law, you have the right to a copy of your eyeglass prescription, so that you can shop for the best value in eyewear.
