What Are the Numbers on the Side of My Glasses Telling Me?

Have you ever wondered what those numbers on the side of your glasses mean? You’re not alone! Many people don’t know what those numbers represent or what they’re used for. In this article, we will go over the meaning behind those numbers and how they’re used to create your perfect prescription glasses.

What Are the Numbers on My Glasses?

The numbers on your glasses refer to your specific eyeglass prescription. These numbers help your optometrist or ophthalmologist determine what type of lenses you need to correct your vision.

The two most important numbers on your glasses are the sphere and cylinder values. The sphere value is used to correct nearsightedness or farsightedness, while the cylinder value is used to correct astigmatism.

Number What it means
OD Right Eye
OS Left Eye
Sphere (SPH) Used to measure nearsightedness (-) or farsightedness (+)
Cylinder (CYL) Used to correct astigmatism
Axis Angle of orientation for the cylinder

SPH (Sphere) Value

The sphere value is the main number used to correct nearsightedness or farsightedness. If your SPH value is negative (e.g. -2.5), it means you are nearsighted. If your SPH value is positive (e.g. +1.5), it means you are farsighted.

The sph value is measured in diopters, which is a unit of measurement that indicates the refractive power of the lens.

CYL (Cylinder) Value

The cylinder value is used to correct astigmatism. Astigmatism is when the cornea of your eye is shaped more like an oval than a round sphere. This causes vision to blur or distort at both near and far distances.

The cylinder value is also measured in diopters and is always a negative number. A higher negative number means you have a greater degree of astigmatism.

Axis Value

The axis value is a number between 0 and 180 degrees that represents the angle of orientation for the cylinder. This number is critical for the manufacturing of your glasses so the cylinders are oriented correctly.

How Are These Numbers Determined?

During an eye exam, your optometrist or ophthalmologist will perform various tests to determine your vision needs. These tests may include a visual acuity test, a refraction test, and other diagnostic tests to determine the health of your eyes.

The refraction test measures the lens power needed to improve your vision. During this test, the optometrist will ask you to look through different lenses and adjust them until you can see the letters on the visual chart clearly.

Based on the results of your tests, your optometrist will determine your prescription and provide you with the numbers necessary to create your glasses.

What Other Numbers Might I See on My Glasses?

In addition to the SPH, CYL, and Axis values, your glasses may also have additional numbers, including:

  • ADD – Used for multifocal lenses to correct presbyopia (difficulty reading small print)
  • PD – Pupillary distance, or the distance between your pupils
  • Prism – Used to correct certain eye alignment issues

It’s important to understand what these numbers mean to ensure you have the correct glasses for your visual needs.


Understanding the numbers on the side of your glasses can help you better understand your prescription and ensure you have the correct glasses for your visual needs. If you have any questions about your prescription or the numbers on your glasses, be sure to ask your eye doctor.

Common Questions and Answers

  • What’s the difference between my left and right eye measurements?

    The measurements of your left and right eye will often differ. This is because each eye may have unique prescription needs. Your optometrist will provide you with the measurements for each eye.

  • What do I do if I notice my vision is getting worse?

    If you notice your vision is getting worse, make an appointment with your eye doctor as soon as possible. They will perform tests to determine if any changes need to be made to your prescription.

  • What if I lose my glasses?

    If you lose your glasses, it’s important to make an appointment with your optometrist to get a new prescription. This will ensure your new glasses will be the correct prescription for your eyes.


  • https://www.medicalnewstoday.com/articles/324622
  • https://www.verywellhealth.com/how-to-read-your-eyeglass-prescription-3422063
  • https://www.americanboardofoptometry.org/blog/understanding-your-glasses-prescription

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