If you've ever looked at your eye prescription and seen numbers under "Cylinder" and "Axis," you may have wondered what they mean. These numbers aren't random—they're specifically for correcting astigmatism, a common condition that affects how light enters your eye.
This guide explains what astigmatism is, how it's diagnosed, and what those prescription numbers actually mean.
What Is Astigmatism?
Astigmatism is a condition where the cornea or lens of the eye is shaped more like a football than a basketball. Instead of being perfectly round, the surface is curved differently in different directions.
What this means: Light entering the eye doesn't focus evenly on the retina. Some parts focus in front of the retina, others behind—resulting in blurred or distorted vision at all distances.
Types of Astigmatism
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Myopic astigmatism – One or both meridians are nearsighted.
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Hyperopic astigmatism – One or both meridians are farsighted.
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Mixed astigmatism – A combination of nearsightedness and farsightedness in different meridians.
Causes
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Genetics – it often runs in families
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Eye injuries or surgeries
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Certain eye diseases
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Can be present from birth or develop later in life
Symptoms and Diagnosis
Common Symptoms
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Blurred or distorted vision (objects may appear stretched or shadowed)
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Eyestrain or fatigue, especially after reading or screen time
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Headaches
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Difficulty seeing at night or with glare
These symptoms can range from mild to severe and often overlap with nearsightedness or farsightedness—which is why a comprehensive eye exam is essential.
How It's Diagnosed
An eye doctor will perform a few simple tests during your exam:
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Visual acuity test – Reading letters from a chart to assess clarity
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Refraction test – Using a phoropter to measure the exact prescription needed
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Keratometry test – Measuring the curvature of the cornea to determine the degree and axis of astigmatism
Correcting Astigmatism
Eyeglasses
Glasses are the most common and straightforward correction. The prescription includes three key components:
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Sphere (SPH) – Corrects nearsightedness or farsightedness
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Cylinder (CYL) – Corrects astigmatism by adding power in specific meridians
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Axis – Indicates the orientation (in degrees, 1–180) where the cylinder power should be placed
💡 Example: CYL -1.25, Axis 90 means astigmatism correction of -1.25 diopters oriented at 90 degrees.
No CYL or AXIS numbers? You likely don't have astigmatism that requires correction.
Contact Lenses
Toric contact lenses are specially designed for astigmatism. Unlike regular contacts, they have different powers in different meridians and must stay in a specific orientation on the eye. They're available in both soft and rigid gas permeable materials.
LASIK Surgery
LASIK reshapes the cornea using a laser, correcting its irregular curvature. It can significantly reduce or eliminate the need for glasses or contacts—but it's not suitable for everyone. A consultation with an eye surgeon is the first step.
Frequently Asked Questions
Can astigmatism be cured?
No, but it can be effectively managed and corrected with glasses, contacts, or surgery.
Is astigmatism hereditary?
Yes. If one or both parents have astigmatism, there's a higher chance their children will too.
Can astigmatism cause headaches?
Yes—especially if left uncorrected. Eyestrain from trying to focus blurry vision often leads to headaches.
Do I need special contacts for astigmatism?
Yes. Toric lenses are designed to correct astigmatism. Regular contacts won't work because they rotate on the eye, while toric lenses stay in a fixed position.
Can I get LASIK if I have astigmatism?
Many people with astigmatism are candidates for LASIK, but it depends on your corneal thickness, prescription stability, and overall eye health. A surgeon can evaluate your eligibility.
Is astigmatism getting worse over time?
For most people, astigmatism is stable. However, it can change slightly with age, injuries, or conditions like keratoconus. Annual eye exams help track any changes.
Disclaimer: This content is for informational purposes only and does not constitute professional medical or optical advice. Always consult your optometrist for personalized diagnosis and treatment recommendations.
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