How to Read a Glasses Prescription

How to Read a Glasses Prescription

If you’ve ever looked at your glasses prescription and felt confused by all the numbers and abbreviations, you’re not alone. Understanding your prescription can help you make informed decisions about your eyewear and ensure your glasses provide the best possible vision correction.

In this guide, we’ll break down the different parts of a glasses prescription and explain what each term means.

Key Components of a Glasses Prescription

A typical prescription includes several abbreviations and numbers that indicate how your lenses should be shaped to correct your vision. Here are the most common terms you’ll see:

1. OD and OS: Which Eye Is Which?

  • OD (Oculus Dexter) – Your right eye
  • OS (Oculus Sinister) – Your left eye
  • Sometimes, you may see OU (Oculus Uterque), which means both eyes.

2. Sphere (SPH): Nearsightedness or Farsightedness

  • The sphere (SPH) value indicates the lens power needed to correct nearsightedness (-) or farsightedness (+).
    • A minus (-) sign means you’re nearsighted (blurry distance vision).
    • A plus (+) sign means you’re farsighted (blurry near vision).
    • If there’s no number (or “Plano”), your vision doesn’t need correction in that eye.

3. Cylinder (CYL) and Axis: Astigmatism Correction

  • Cylinder (CYL) measures the lens power needed to correct astigmatism (an irregularly shaped cornea or lens).
    • If this section is blank, you don’t have astigmatism.
    • Like SPH, it can be a (+) or (-) value.
  • Axis is a number between 1 and 180 that shows the orientation of the astigmatism correction.

4. Add (Near Vision Power for Bifocals/Progressives)

  • The Add value is for people who need reading glasses or multifocal lenses (bifocals/progressives).
  • It’s always a positive number (e.g., +1.50, +2.00) and is the same for both eyes.

5. Prism and Base (For Eye Alignment Issues)

  • Some prescriptions include prism correction (measured in diopters) to help with double vision or eye misalignment.
  • Base indicates the direction of the prism (e.g., “BU” for base up, “BD” for base down).

Sample Prescription Breakdown

Here’s an example prescription and what it means:

Eye SPH CYL Axis Add
OD -2.00 -1.25 180 +1.50
OS -1.75 -0.75 170 +1.50
  • Right Eye (OD):
    • -2.00 SPH: Nearsighted, requiring 2.00 diopters of correction.
    • -1.25 CYL, Axis 180: Astigmatism correction at 180 degrees.
    • +1.50 Add: Additional power for reading.
  • Left Eye (OS):
    • -1.75 SPH: Nearsighted, requiring 1.75 diopters.
    • -0.75 CYL, Axis 170: Astigmatism correction at 170 degrees.
    • +1.50 Add: Additional power for reading.

Why Understanding Your Prescription Matters

  • Ensures you order the correct lenses online.
  • Helps you discuss vision needs with your optometrist.
  • Allows you to recognize changes in your vision over time.

Final Tips

  • Always consult your eye doctor if you have questions.
  • Prescriptions expire—check the date to ensure yours is still valid.
  • Different countries may format prescriptions slightly differently.

Now that you know how to read your glasses prescription, you can confidently choose the right lenses for clear, comfortable vision!

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