Keratoconus is a progressive thinning of the cornea and is the most common cornea dystrophy in the United States, according to the National Eye Institute. In fact, it affects one in every 200 Americans. It happens when the middle of the cornea thins and bulges outward, gradually forming a rounded cone shape. This changes the cornea’s refractive power producing astigmatism, or distortion, and nearsightedness, or blurriness.

Warning Signs & Symptoms

Keratoconus symptoms often start in people in their late teens and early 20s. The earliest symptom is a subtle blurring, shadowing or doubling of vision that is not correctable with glasses or contact lenses. It usually affects both eyes, but is frequently more severe in one eye than the other. As the astigmatism worsens, patients must rely on specially fitted contact lenses to reduce the distortion and provide better vision. It is crucial for the lens to fit because a poorly fitting lens could further damage the cornea and make wearing a contact lens intolerable.


Keratoconus can be diagnosed in an eye exam. To determine the shape of the cornea, your eye doctor may conduct two additional tests: keratometry and computerized corneal mapping.

Treatment and Procedures

In most cases, the cornea will stabilize after a few years without ever causing severe vision problems. But in about 10 to 20 percent of people with keratoconus, the cornea will eventually become too scarred or will not tolerate a contact lens. If either of these problems occurs, a corneal transplant may be needed. Newer surgical procedures and treatments involving precise application of ultraviolet radiation with riboflavin can sometimes stabilize, and even reduce, the signs and symptoms of keratoconus.


The cause of keratoconus is unknown, so there are no preventive measures.

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