Astigmatism severity scale

The astigmatism severity scale measures the degree of refractive error in your eye. Refractive errors prevent light from focusing directly on the retina, so they can cause blurry or distorted vision. Before we get into the nuts and bolts of the scale, let's dive into a refresher on astigmatism and its symptoms.

Eyeballs are supposed to be round, but in many people, they're oval or egg-shaped. This is known as astigmatism. Although astigmatism isn't dangerous, it can interfere with normal vision, especially if you're on the high end of the scale (one example where a higher score isn't a positive thing).

Making things even more complicated, astigmatism doesn't affect everyone the same way. Some people experience no symptoms at all (lucky ducks). Others experience blurriness or poor night vision.

If you have astigmatism, you deserve to know how severe it is. Learn more about how eye care professionals use the astigmatism severity scale to recommend appropriate eyewear.

Introducing the astigmatism severity scale

The astigmatism severity scale has three levels: mild, moderate, and extreme (high). Three components determine exactly how severe your astigmatism is:

• Sphere: Sphere indicates the lens power needed to correct farsightedness or nearsightedness. A plus sign shows you're farsighted, while a minus sign (negative number) means you're nearsighted. Hey, nobody's perfect.

• Cylinder: On the astigmatism severity scale, cylinder measures the degree of astigmatism. The more your eye looks like a football, the higher your cylinder measurement will be. Unfortunately, football-shaped eyes don't come with NFL-level fame.

• Axis: The axis describes the location of the abnormal curvature. This helps determine how much to rotate your corrective lenses to eliminate distortion. On the astigmatism severity scale, axis measurements range from 0-180 degrees.

Here's an example: -1.00, -1.25, 180

In this example, -1.00 is the lens power (sphere), -1.25 is the cylinder value, and 180 is the orientation needed for the cylinder power of your corrective lenses (axis).

Eye care professionals use a unit of measurement known as the diopter to determine the severity of astigmatism. A diopter measures the focusing power of glasses or contact lenses.

Mild

Mild astigmatism is when the curvature of the eye measures fewer than 1.0 diopter. If you wish upon a four-leaf clover, you may not have any symptoms. However, mild astigmatism can cause blurry vision or distortion when you look at certain objects.

If you have mild astigmatism, soft toric lenses may be a good fit for your needs. Toric lenses have a unique shape, so they can correct vision issues caused by the abnormal shape of your eye. 1-800 Contacts offers these options:

• 1-DAY ACUVUE® MOIST® for Astigmatism

• AIR OPTIX® Plus HydraGlyde® for Astigmatism

• Biofinity® Toric

Moderate

So, what's the severity level of astigmatism when it's classified as moderate? Easy. It's a diopter measurement of 1.0- 2.0. You might need glasses or contact lenses once you cross the 1.5 threshold, as moderate astigmatism can cause distortion, blurriness, eyestrain, and squinting.

Soft toric lenses are also a good fit for users with moderate astigmatism. Top brands include:

• ACUVUE OASYS® for Astigmatism

• Bausch + Lomb ULTRA for Astigmatism

• Biotrue® ONEday for Astigmatism
  
  

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If you prefer to wear eyeglasses, look for a pair with an antireflective coating. This coating reduces glare, so it may eliminate halos or prevent light scattering.

Antireflective coating also makes it safer and easier to drive at night. Instead of avoiding night driving like a vampire avoids garlic, you can take the wheel with confidence. Anti-glare coating comes standard with many of the eyewear options offered by The Framery. Here are a few of our favorites:

• Lenox

• Norma

• Peyton

• Riley

• Twila

Extreme (high)

Astigmatism is classified as severe with any diopter measurement above 2.0. However, some eye care professionals distinguish high astigmatism from extreme astigmatism. High is a diopter measurement ranging from 2.0- 4.0, while extreme is a diopter measurement above 4.0.

If you prefer contacts, look for high-prescription toric soft lenses or rigid gas-permeable (RGP) lenses. RGPs are ideal for high prescriptions, and they're also extremely durable. 1-800 Contacts offers these options:

• Biofinity XR Toric

• Proclear® Toric XR

XR stands for "extended range," which means that a contact was designed for users with extreme nearsightedness or farsightedness.

If you prefer eyeglasses, you need a full-frame style that sits securely on the bridge of your nose. Avoid wraparound styles, as they can make astigmatism-related distortion worse. Check out these options from The Framery:

• Chantel

• Conway

• Dallas

• Heidi

With a diopter measurement above 4.0, you may not be able to achieve 20/20 vision. Ask your eye care professional if surgery makes sense. Refractive surgery reshapes the cornea, so it can help improve your vision even if you have an extremely high diopter measurement.

Why the scale is important for contacts and glasses

The astigmatism severity scale is important for contacts and eyeglasses because it helps your eye care professional understand what kind of corrective lenses you need. For example, if you have severe astigmatism, you may benefit from extended-range toric lenses.

To determine your diopter measurement, an eye care professional uses a keratometer. This tool measures the reflection of light, making it possible to diagnose refractive errors. They may also conduct a visual acuity test and a refraction test.

The visual acuity test involves looking at a chart and reading the smallest characters that you can see clearly — no hidden messages, no tricks, just reading a few letters and numbers. The refraction test determines how light bends as it moves through your corneas and lenses.

How to measure the severity of your astigmatism

Astigmatism is extremely common, but it can affect your ability to see clearly. The good news is that corrective lenses can help eliminate blurriness, distortion, and other symptoms. If you have extreme astigmatism, you may even qualify for surgery to improve your vision.

Best of all, 1-800 Contacts and The Framery have a wide selection of lenses ideal for users with astigmatism. Find your preferred brand today.

Did you know you can order contacts online? 

Say goodbye to trips to the eye doctor and hello to convenience! With 1-800 Contacts, you can easily order your contact lenses online and have them delivered straight to your door. Plus, our online vision exam makes it simple to get the prescription you need without leaving home. And the best part? You’ll save money on your first order with 1-800 Contacts. It’s never been easier to get your contacts!

Original publish date: 4/8/2024

Updated date: 3/31/2026