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How to Read Your Eyeglasses Prescription

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You just had an eye exam and your optometrist gave you a new vision prescription for eyeglasses. Problem is, you can’t make sense of it. There’s a bunch of unfamiliar acronyms and numbers. You know all those numbers relate to the lenses that you need to wear to see clearly, but what does each one mean?

The simple explanation is that those numbers refer to the lens powers you need to correct your eye’s refractive error – so you can enjoy crisp vision instead of the blurred vision you’ve had until now.

If it’s been a while since your last eye exam, contact one of our Eagle Mountain Family Eye Care offices in Fort Worth, , , , , and , Texas, to book an appointment with our eye doctor. We want you to have a sharp view of the world, and we’ll check your visual acuity thoroughly to issue your up-to-date, precise vision prescription for eyeglasses.

A Breakdown of Your Eyeglasses Prescription

Let’s go through the significance of the letters and numbers on your prescription:

  • OS and OD: these are Latin abbreviations that stand for oculus sinister and oculus dextrus, respectively. (If your prescription also says OU, it refers to oculus uterque, for both eyes.)
  • Numbers: generally, the greater the number is away from zero, the worse your vision – and the more vision correction you need. That translates into a stronger prescription.The numbers represent diopters (sometimes abbreviated “D”), which is the standard unit for measuring the focusing power of the lens your eye requires to see clearly.
  • +/- :  if there is a plus/+ sign before the number, it means you are farsighted; if there is a minus/- sign before the number, it means you are nearsighted.
  • S x C x AXIS: if you have astigmatism, there will be three additional numbers on your prescription-
    • SPH (S) refers to the spherical part of your prescription, which is the degree of nearsightedness or farsightedness.
    • CYL (C) refers to the cylinder (the astigmatism), and it can be a positive or negative number; it measures your degree of astigmatism in diopters. The higher this number, the more astigmatism (= the more your cornea is shaped like an ellipse, instead of a globe).
    • Axis is a number from 0 – 180 that reveals the orientation of the astigmatism, describing exactly where the difference in curvature is occurring.
  • ADD: this is a correction factor for when you need a different prescription for near vision, such as for presbyopia. This number is always a plus/+.
  • PD: stands for interpupillary distance. It is a measurement of the distance between the center of one eye to the center of your other eye, and it is an important piece of information. PD ensures that your eyes match up with the optical center of your eyeglasses lenses.

People often worry when they see a major difference in the numbers for the right eye to be very different from the left eye. However, this is quite common.

Check the date on your eyeglasses prescription

There’s one more important number on your prescription - the date of issue! Now that you’re fully informed about how to read your eyeglasses prescription, it’s time to make sure you had an eye exam in the last year, and that your lenses are truly optimizing your vision. Book an annual eye exam with our eye doctors in Fort Worth, , , , , and , Texas, to ensure your eyeglasses prescription is accurate!


At Eagle Mountain Family Eye Care, we put your family's needs first. Talk to us about how we can help you maintain healthy vision. Call us today: 817-769-6601 or book an appointment online to see one of our Fort Worth eye doctors.

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