Guide to Reading Your Eyeglass Prescription

Getting a new eyeglass prescription can feel a little like receiving a note written in code. Rows of abbreviations, plus and minus signs, and columns of numbers, what do they all mean? At Crystal Clear Optometry in McAllen, TX, we believe understanding your prescription is an important step toward taking charge of your vision health. Here’s a simple breakdown.

The Basics: OD and OS

At the top of your prescription, you’ll often see the abbreviations OD and OS.

•             OD stands for oculus dexter, or your right eye.

•             OS stands for oculus sinister, or your left eye.

Sometimes you may see OU (oculus uterque), which refers to both eyes.

Sphere (SPH): Nearsighted or Farsighted?

The SPH value tells you the lens power needed to correct your vision.

•             A minus sign (-) means you’re nearsighted—distant objects appear blurry.

•             A plus sign (+) means you’re farsighted—close-up vision is more challenging.

The higher the number, the stronger the correction.

Cylinder (CYL) and Axis: Astigmatism

If you have astigmatism, a common condition where the cornea is shaped more like a football than a sphere, your prescription will have a CYL value and an Axis number.

•             CYL indicates the lens power needed to correct astigmatism.

•             Axis is a number between 1 and 180 that tells the lab exactly how to align that correction.

Add Power: For Reading or Multifocals

If you need help seeing up close in addition to your distance correction, your prescription may have an ADD value. This is common for multifocal or progressive lenses and is the extra magnifying power for near tasks like reading or using a phone.

Prism: Special Adjustments

Occasionally, a prescription will include prism correction, measured in prism diopters. This helps correct eye alignment problems, reducing double vision or eye strain.

Putting It All Together

Each part of your prescription works together to give you the clearest, most comfortable vision possible. Understanding what those numbers mean empowers you to make informed choices about your eyewear. Whether you’re selecting frames, choosing lens upgrades, or discussing options with your optometrist.

Call Our Optometrist near You to Learn More About Your Prescirption

Your prescription isn’t just numbers. It’s a personalized map to better vision. If you’d like help understanding yours or want to ensure your eyewear is perfectly matched to your needs, schedule a visit with Crystal Clear Optometry in McAllen, TX. We’re here to make every detail crystal clear. Call us today at (956) 687-6567.