The prescription your optometrist writes for your eyeglasses might be confusing, but it tells you a lot about your vision. Here's how to make sense of the information you see.
Even if you’ve worn glasses for years, you may have never looked carefully at your eyeglass prescription before. This piece of paper contains a bunch of numbers and abbreviations. And it can help you see the world in a much clearer way.
Want to learn how to crack the code of what it all means? Here’s a quick breakdown that will help you do just that.
Has it been a while since your last eye exam? Now’s the time to book an appointment!
How Your Eye Doctor Examines Your Vision
To get an accurate prescription, your optometrist will first ask you to look into a box known as an autorefractor. You will see a little picture inside the machine, often of a farmhouse, hot air balloon, or an apple. When you look at the picture, the machine automatically calculates how good — or bad — your vision is.
And beyond the classic eye chart test, there will also be other tests that check for other issues such as the amount of pressure in your eye, how healthy your pupils are, how well your eyes move, and your depth perception. Your eye doctor will then use this information to help determine your prescription.
Staying on top of your annual eye appointments can help catch any vision changes or eye problems before they’ve progressed into a more serious problem.
Press play to learn more about what to expect during your eye exam:
Eyeglass Prescription Abbreviations and Terms
When you receive your prescription, it should have a grid with a series of abbreviations running across the top of it. Here’s what each of those mean.
OD, OS, and OU
These are abbreviations for Latin terms for your eyes. O.D. is short for oculus dexter, and that’s your right eye. O.S. stands for oculus sinister, and that’s your left one. If you see O.U. on the prescription, that refers to both of your eyes. That’s the abbreviation for oculus uterque.
SPH (Sphere)
Moving over one column to the right, you’ll see the initials SPH. That stands for sphere. The numbers in this column tell you how well you see objects up close and far away in each eye. The minus sign represents nearsightedness, and the plus sign means farsightedness.
Here’s an example: If you see the number –2.00 after O.D. in the SPH column, it means your prescription calls for two diopters. That’s a unit that eye doctors use to measure the lens power to correct the nearsightedness in your right eye. Two diopters means you’re only mildly nearsighted.
The further your number is away from zero on either the minus or plus side, the stronger your prescription is.
CYL (Cylinder)
Next up is CYL, which stands for cylinder. This tells you if you have astigmatism, which means your eye isn’t totally round, which can make things look blurry. If you don’t see a number here, you don’t have astigmatism. But if you do, the number you see represents how much lens power is needed to correct it.
Axis
Axis is to the right of cylinder. This term refers to the direction of the astigmatism on your eye. The axis, which ranges from 1 to 180, tells you if your astigmatism is straight up and down 90 degrees, across your cornea at 180 degrees, or somewhere in between.
Prism
You may see the word “Prism” but very few prescriptions include it. Prism lenses are typically used to fix rare issues with eye alignment, such as double vision.
ADD Power
If you wear progressives or bifocals, you’ll also want to better understand what add power means. This indicates if you need more magnifying power in the lower part of a bifocal lens to see better up close.
Add power becomes a factor in your 40s and beyond when you start to have trouble focusing on close-up tasks, like reading. It’s due to a condition called presbyopia, and it’s a normal part of aging.
Last we checked, 128 million people in the United States have presbyopia, which is a Latin term that means “old eye.” But don’t take that terminology personally. It’s nothing a prescription tweak can’t help correct.
Additional Information
This is the section of the prescription where your eye doctor can recommend things like eyeglass brands, lens coatings, or lens materials. (Here’s where you can learn more about your lens choices.)
Expiration Date
Finally, pay close attention to the expiration date on your eyeglass prescription. An eyeglass prescription typically expires after one or two years. That’s because your eyes change enough in that period to need a new prescription.
Press play to understand more about your eye exam results:
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