Updated: Jul 29, 2019
When you leave your eye exam and are looking over your eyeglass prescription, you're probably wondering, "What on earth do all these numbers mean?"
First, let's start with some vocabulary:
1. Hyperopia - "far-sighted", you see things better far away without glasses
2. Myopia - "near-sighted", you see things better up close without glasses
3. Astigmatism - you might notice distortion/blurry vision both far away and up close
4. Presbyopia - you need reading glasses
Second, you have a prescription for each eye. You'd think we'd identify your right and left eye by the letters "R" and "L" on your prescription, but we unfortunately do not. "OD" stands for oculus dexter, which indicates your right eye. "OS" stands for oculus sinister and indicates your left eye.
Third, your prescription is split into four categories, Sphere, Cylinder, Axis, and Add (see above). The first, second, and fourth numbers are measured in a unit called diopters, and the third number (axis) is measured in degrees. An eye without any prescription has 0 diopters.
Sphere, the first number, indicates if you have hyperopia or myopia. If you have hyperopia, you will have a "+" sign before first number (eg. +1.00). If you have myopia, you will have a "--" sign before the first number (eg. -1.00). The higher the number, the stronger your prescription.
The second and third numbers of your prescription, "cylinder" and "axis", refer to astigmatism. If you do not have astigmatism, these boxes will be left blank. Cylinder refers to the amount of astigmatism and axis indicates where on the eye the astigmatism is located (see prior blog post on astigmatism).
The fourth box indicated by "Add" indicates the reading prescription, if you have one, otherwise this box is left blank, and this number will typically have a "+" sign in front of it.
So, if we're trying to interpret the prescription indicated above, this person has myopia and is near-sighted in both eyes, has some astigmatism, and they do not have a reading glass prescription.
If you ever have any questions or concerns about your prescription, ask your eye doctor!