Updated on  February 5, 2024
2 min read

What Does Axis Mean for Glasses Prescriptions?

6 sources cited
Vision Center is funded by our readers. We may earn commissions if you purchase something via one of our links.

What Does Axis Mean for Glasses Prescription?

Eye doctors examine eyes to diagnose vision problems and refractive errors. One aspect that eye doctors consider is the eye axis. 

The axis indicates the position of astigmatism in the eyes. It doesn’t indicate the strength of an eyeglass prescription.

The axis is the lens meridian that does not contain cylinder power. It’s defined by a number between 1 and 180 degrees.

  • The number 90 represents the eye’s vertical meridian
  • The number 180 represents the horizontal meridian
How to tell eyeglass prescription

Cylindrical Power in Astigmatism

When an eyeglass prescription has cylindrical power (CYL value), the axis value directs where to place the power in the lenses. This allows people with astigmatism to see better. 

In eyeglass prescriptions, optometrists will note both the cylinder power and axis. The cylinder power is the strength of astigmatism correction needed. If the axis is 180 degrees, you may see it noted as x180.

Cylindrical power and axis work in tandem. The axis denotes the orientation, while the cylindrical power indicates the amount of correction needed.

Sphere Value Vs. CYL

The sphere value of a prescription works differently than the CYL since it measures nearsightedness or farsightedness. Sphere values indicate the amount of correction needed for either condition.

The sphere value doesn’t require an axis to indicate its placement in the lenses. Eye doctors will note this power separately in an eyeglass prescription.

Where to Buy Glasses + Contacts

Best Overall: Warby Parker

Fastest Delivery: EyeBuyDirect

Also Great: Liingo

Best Place to Buy Contacts: 1800 Contacts

What is a “Normal” Eye Axis?

Those with a “normal” eye axis will not see CYL values in their eyeglass prescriptions. This is because these people don’t have astigmatism. 

People with a normal eye axis have strong and clear vision. The light falls at the right place on their retina.

More Reading

Summary

Axis refers to the position of astigmatism in the eyes. The cylinder power (CYL value) is the lens power for astigmatism. If you don’t have CYL values listed in your prescription, then you don’t have astigmatism. Your eye doctor can determine these numbers during an eye check-up.

Best Places to Buy Glasses

Best Overall

Warby Parker has stylish, high-quality frames at affordable prices.

Also Great

Liingo Eyewear is another great option to buy glasses online.

Best on a Budget

EyeBuyDirect has a wide variety of budget frames starting at $6.

Best Places to Buy Contacts

Best Overall

1-800 Contacts is our #1 recommendation to buy contacts online.

glasses usa logo
Also Great

GlassesUSA has a huge selection of contacts, glasses, & sunglasses.

Updated on  February 5, 2024
6 sources cited
Updated on  February 5, 2024
  1. Gilbert, M. L. “What Are ‘Normal’ Results of an Eye Exam? Other than 20/20, What Are Normal Axis and Sphere Numbers?” American Academy of Ophthalmology, 2018.
  2. Porter, D. “How to Read an Eyeglasses Prescription.” American Academy of Ophthalmology, 2020.
  3. Porter, D. “What Is Prism Correction in Eyeglasses?” American Academy of Ophthalmology, 2019.
  4. “Why Has Myopia Become More Common?” Pacific University Oregon, 2019.
  5. “What Do Astigmatism Measurements Mean?” American Academy of Ophthalmology, 2021.
  6. Navarro, R. “The Optical Design of the Human Eye: a Critical Review.” Journal of Optometry, 2009.
The information provided on VisionCenter.org should not be used in place of actual information provided by a doctor or a specialist.