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What is Regular vs. Irregular Astigmatism?

You may have heard your eye doctor talk about astigmatism. It’s actually quite common and can be diagnosed as a routine part of a comprehensive eye exam. It means there is an imperfection in the curvature of the eye’s cornea or lens. But there are different types of astigmatism and that can cause confusion. Here, we focus on the cornea, the clear outer layer of the eye, and explore the differences between regular astigmatism and what’s known as irregular astigmatism.

What is regular astigmatism?

Regular astigmatism is when the curvature of the eye is not completely round. With this type of astigmatism, the eye is curved more in one direction than another – think football shaped versus basketball shaped. Regular astigmatism distorts vision, making objects from near to far appear blurry or stretched. It is possible to have an astigmatism along with other refractive errors such as nearsightedness (myopia) or farsightedness (hyperopia).

What is irregular astigmatism?

Irregular astigmatism is similar to regular astigmatism in that the curvature of the eye’s surface is not perfectly round, but where it differs is that instead of the curvature being evenly shaped (mostly in one direction), it is uneven, or curved in multiple directions. For example, it could be steeper towards the bottom and less so towards the top. It could even have multiple configurations. With irregular astigmatism, it is more difficult to describe how uneven the eye is shaped. An eye doctor, however, can diagnose and measure irregular astigmatism using advanced scans of the front of the eye, such as corneal topography, which provides a 3D map of the shape and curvature of the eye.

Irregular astigmatism, which is less common than regular astigmatism, is often associated with prior ocular surgeries, such as radial keratotomy (RK) trauma to the eye, or eye conditions such as keratoconus. Similar to regular astigmatism, irregular astigmatism can cause vision to appear blurry or distorted. Patients with irregular astigmatism can also be described as having a Complex Cornea.

How is astigmatism treated?

For patients with regular astigmatism there are several options available to effectively correct their vision including contact lenses, glasses, and laser vision correction.

For patients with irregular astigmatism, treatment can be more complex as each cornea is unique.  Seeking out a specially trained physician with expertise in treating corneas can help patients with irregular astigmatism receive the latest treatment options and help them achieve their best personal vision.