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What Is Keratoconus?

Keratoconus is an eye disease characterized by bulging forward of the front surface of the eye due to abnormal thinning of the cornea.


The cause of keratoconus is not fully understood, but risk factors include eye rubbing, allergies, and heredity.

Some research suggests disruption of normal levels of certain enzymes and other substances in the cornea (including compounds that influence inflammatory responses) is associated with keratoconus, but the underlying cause of this disruption is unclear.

Keratoconus is abnormal thinning and bulging forward of the cornea.

The reported prevalence of keratoconus varies widely based on geography and methods used to diagnose the eye disease. One of the most-cited studies of the epidemiology of keratoconus in the United States found keratoconus affects roughly 54 people per 100,000 population (about one in 2,000 people).

However, a recent study in the Netherlands found that the estimated prevalence of keratoconus in the general population was 265 cases per 100,000 (one in 377), which is significantly higher than values reported in previous studies.

Keratoconus generally begins in a person's teens or early 20s. It can affect one or both eyes. In the Netherlands study mentioned above, 60.6 percent of diagnosed patients were male.

Left untreated, keratoconus is progressive: the cornea eventually becomes irregularly cone-shaped, causing blurred vision that cannot be corrected with eyeglasses or conventional contact lenses. Keratoconus also can cause scarring of the cornea that further decreases best-corrected visual acuity.

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Dr. Gary HeitingAbout the Author: Gary Heiting, OD, is senior editor of AllAboutVision.com. Dr. Heiting has more than 25 years of experience as an eye care provider, health educator and consultant to the eyewear industry. His special interests include contact lenses, nutrition and preventive vision care.

Page updated February 2018