How to Read and Understand the Numbers on Your Eyeglass Prescription in New Berlin, WI

What Do the Numbers on an Eyeglass Prescription Mean?

Eyeglass prescriptions are written in a specialized format that can look confusing at first glance. These numbers help determine the lenses that will work best to correct your vision. For residents of New Berlin, WI, being able to read your prescription empowers you to make informed decisions about your eye health and compare options if you ever need new glasses.

Prescriptions include a series of values, usually labeled in columns for each eye. They address nearsightedness, farsightedness, astigmatism, and sometimes additional corrections. Understanding what each value represents helps you decode your prescription with confidence.

What Is the Difference Between OD and OS?

OD and OS are Latin abbreviations found on nearly all vision prescriptions. These help specify which eye the values refer to.

• OD (Oculus Dexter): Right eye
• OS (Oculus Sinister): Left eye

Sometimes you’ll also see “OU,” meaning “each eye” (both). The information for OD and OS is typically shown in separate rows, with columns for different types of correction.

How Is Nearsightedness (Myopia) or Farsightedness (Hyperopia) Indicated?

The first number assessed for each eye is the Sphere (SPH) value. This tells you if you need correction for nearsightedness or farsightedness, and by how much.

• A negative (-) sign in this column means you are nearsighted—distant objects appear blurry to you.
• A positive (+) sign indicates farsightedness—you see distant objects more clearly than near ones.

The higher the absolute value, the stronger the prescription for each condition. For example, a sphere value of -4.00 means significant nearsightedness, while +1.50 signals mild farsightedness.

What About Astigmatism—What Are Cylinder (CYL) and Axis?

Astigmatism is a common condition where the eye’s shape causes blurred vision. It’s addressed in your prescription with two numbers: Cylinder (CYL) and Axis.

• CYL (Cylinder): Indicates the amount of astigmatism correction needed. This value may be positive or negative.
• Axis: Specifies the lens orientation (from 1 to 180 degrees) that corrects the irregular curve of your cornea or lens.

If there is no astigmatism correction needed, one or both of these numbers may be blank or omitted.

What Does ADD Mean on a Glasses Prescription?

ADD (Addition) comes up for people needing multifocal lenses, such as bifocals or progressive lenses. It refers to the extra magnifying power required for close-up tasks like reading—something that often changes with age due to a condition called presbyopia.

The ADD value is always positive and typically ranges from +0.75 to +3.00. For local adults, especially those over age 40, this extra value helps customize lenses to match both distance and reading needs.

What Is PD and Why Is It Important?

PD stands for Pupillary Distance—the space in millimeters between the centers of your pupils. This measurement ensures the lens’ optical center aligns with your eyes, which is critical for comfortable, effective vision correction.
Most prescriptions don’t print PD automatically; it may be measured when you purchase new glasses in New Berlin or manually upon request. Children and adults alike benefit from an accurately measured PD.

Why Do Some Prescriptions Have Prism Values?

Prism correction is less common but important for some people. It’s used to address eye alignment issues that cause double vision or significant eye fatigue. The prism is measured in diopters (Δ), with an additional direction for the base (e.g., base up, base in).
If you see prism values on your prescription, it generally means your optometrist found a need to adjust how images are aligned between your two eyes.

Are There Special Notations Residents Should Recognize?

Occasionally, letters or symbols might appear that aren’t immediately intuitive, such as “DS” (diopters sphere only) or “Plano” (no correction needed). These refer to special situations and are used for clarity.

• DS: Only spherical correction is prescribed; astigmatism is not present.
• Plano: No correction required for that eye.

In the New Berlin area, it’s also common to find “NV” or “DV” (near vision, distance vision) on multifocal prescriptions.

How Accurate Are These Numbers Over Time?

Eyeglass prescriptions are valid for a specific period—typically up to two years for adults, but requirements may vary locally for children due to changing vision. Because vision can gradually shift, especially for youth and older adults in the community, regular eye exams are recommended to keep prescriptions current.

Can I Use Sunglass or Over-the-Counter Reading Glasses if I Know My Numbers?

While it’s tempting to try matching your prescription to ready-made glasses, over-the-counter options usually don't address astigmatism or include your PD. For customized vision needs—especially with more complex prescriptions found in families and older adults around New Berlin—a personalized prescription ensures the best visual comfort and eye health.