A visit to the eye doctor really isn’t as big of a deal as going to the dentist, for example. There’s no drilling, definitely no poking, and the entire experience is relatively painless. Aside from the embarrassment of only making your way to line two on the eye chart, the visit typically breezes by without incident until you’re handed your eyeglasses prescription.
Understanding how to read your eyeglasses prescription can be daunting. After all, you watched your optometrist furiously jot down abbreviations, letters, numbers—and possibly hieroglyphics—right in front of your eyes. What could it all mean?
Eyeglass Prescription Abbreviations
Let’s start with the most basic element of your eyeglass prescription: names for your eyes. Some prescriptions will say ‘OD’, ‘OS’ or ‘OU’.
- OD stands for the Latin term, oculus dexter, also known as your right eye.
- OS is short for oculus sinister, or left eye. Simple right? Some doctors keep it extra simple and use RE (right eye) or LE (left eye).
- OU, oculus uterque, means ‘both eyes’.
But wait, there’s more than meets the eye. Here’s the scientific side of eyeglass prescriptions.
First, everything regarding the strength of your eyesight, represented by SPH (sphere) is measured in diopters (D).
- If you notice a plus sign (+) next to the SPH abbreviation, that means you’re farsighted.
- A negative sign (-) means you’re nearsighted.
- CYL (cylinder) means you have astigmatism. Again, if you see a plus sign (+), you have a farsighted astigmatism, and of course, a minus sign (-) means nearsighted astigmatism.
The Axis and Add of Eye Prescriptions
Next is the axis, which identifies the section of your lens that needs assistance in correcting the direction of your vision, measured from 1-180. If you have astigmatism, you’ll notice an axis measurement on your eyeglasses prescription.
Finally, you’ll also see ‘add’ on your prescription, which is the added magnifying power required in your lenses, and will typically range from +0.75 to +3.00 diopters.
Ready for a crash course? Here’s a sample eyeglass prescription and what it all means.
OD= -4.00 SPH +3.00 add
OS= -2.00 -0.50 x 180 +3.00 add
If this were your eyeglass prescription, you have been prescribed -4.00 diopters to correct your right eye, and you have no astigmatism, which is why you see SPH next to the measurement, meaning that only spherical power is being added to that lens.
Your left eye is prescribed -2.00 diopters along with -0.5 diopter cylinder to correct astigmatism. The axis measurement is 180 and will add -0.5 diopters to correct astigmatism. Both eyes are getting added power of +2.00 to correct the loss of power due to age, hereditary reasons or simple downgraded vision.
There’s more involved under rare circumstances, but this covers the long and short of it all. The next time you receive a new eyeglasses prescription, give it a shot. Or, if you’re like the rest of us, take your doctor’s word for it and focus on choosing those stylish frames.