Keratoconus & Astigmatism: What’s the Difference?

Keratoconus & Astigmatism: What’s the Difference?

by Brian Chou, OD, FAAO, FSLS

April 11, 2024

If you have keratoconus, an eye doctor has almost assuredly told you that you have astigmatism. Keratoconus and astigmatism can get confused. What are they and how are they related to one another?

The Short Explanation

Keratoconus is an eye disease which distorts vision and affects one in several hundred. By comparison, astigmatism is not an eye disease but describes how light bends through the eye in a disordered way. Astigmatism is very common, with roughly half of humans having measurable astigmatism. Most astigmatism is “regular” where light is bent symmetrically in one direction more than another. However, the astigmatism in keratoconus is also characterized by “irregular astigmatism”, where the light bending is asymmetric and often smeared in multiple directions.

How They Relate

Everyone with keratoconus has astigmatism. This is because keratoconus is characterized by a distorted cornea – the clear front dome of the eye. In keratoconus, light bends into the eye in a complex and irregular way. The mainstay of vision correction in keratoconus is custom rigid surface lenses, including scleral contact lenses. However, most with astigmatism do not have keratoconus. In other words, the majority of people with astigmatism get good outcomes with the traditional vision correcting methods of glasses, disposable contact lenses, and laser vision correction. Of course, if you have keratoconus, vision correction is usually more novel and complex.



ReVision Optometry is a referral-based practice in San Diego providing contact lens services for patients with keratoconus. To schedule an appointment, request your appointment online, or call our office at 619.299.6064.