When you leave the eye doctor's office with a prescription for glasses, you may be wondering just what all those numbers and columns on the prescription mean. It isn't difficult to crack the code, though. Knowing how to read your prescription can make it easier for you to learn about the different methods of vision correction that are appropriate for your condition.
This is a sample of a typical prescription. It lays out the degree of correction needed in the right eye and the left eye. It also indicates if the patient has astigmatism.
This individual has mild myopia in both eyes (-1.25 diopters in R and L).
Some doctors use the medical terms for right eye and left eye: oculus dextrus and oculus sinister. So if your prescription reads o.d. and o.s. rather than R and L, you'll know what that means.
The measurement used in eye prescriptions is the diopter. Three measurements are taken during the eye exam: sphere, cylinder and axis.
The sphere measure tells the eye doctor whether light focuses on the retina, in front of the retina or behind the retina. Negative diopters indicate myopia, or nearsightedness. Positive diopters indicate hyperopia, or farsightedness. The higher the number, the stronger the prescription.
The cylinder measurement indicates whether or not the patient has astigmatism. If any number appears in the cylinder column, then some astigmatism is present. The higher the number, the more severe the astigmatism.
This individual has mild astigmatism in the left eye and none in the right eye (-.25 diopters in left).
If astigmatism is present, then an axis measurement is also necessary. This measurement indicates the location of the astigmatism on the eyeball.
Now, test yourself by reading this prescription:
To see if you were right, click here to get a description of this patient's eyesight.