Eye Facts

Keratoconus (Cone-Shaped Cornea)

What is Keratoconus?

Keratoconus is an eye condition in which the shape of the cornea becomes distorted. The cornea is a clear structure that covers the front of the eye and allows light to enter the eye. In a healthy eye, the cornea curves like a dome. In an eye with keratoconus, the center of the cornea slowly thins and bulges, so that it sags and has a cone shape (see illustration).

In keratoconus, the posterior layer may tear in rare cases. When this happens, the cornea may suddenly become swollen with water (termed hydrops).Wrinkles and scars may also form on a keratoconus cornea.


Keratoconus illustration

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How does keratoconus interfere with vision?

People with keratoconus may lose vision in two ways:

l. From distortion of the cornea: Seeing through a misshapen cornea is like taking pictures with a camera whose lens has an irregular (not smooth) surface. Parts of the picture or field of vision are in focus and parts are out of focus. This visual problem is called irregular astigmatism.

2. From scarring or swelling of the cornea: Seeing through a scarred or swollen cornea is like taking pictures with a camera with a dirty or cloudy lens. The picture or vision is blurred.

How common is keratoconus?

Keratoconus occurs in 50 to 230 per 100,000 population.

Who gets keratoconus?

Keratoconus has been found in all races and in both sexes but affects women more often. It occurs more frequently in patients with Down’s syndrome, allergies or congenital amaurosis (a rare form of blindness at birth). Keratoconus may also develop in persons who have worn contact lenses for a long time and who often rub their eyes with too much force.

What are the symptoms of keratoconus?

The symptoms of keratoconus usually start in puberty (in the teens) and may progress for the next 10 to 20 years. The early symptoms of keratoconus include decreased vision and worsening nearsightedness. Sometimes keratoconus is diagnosed when sudden swelling (hydrops) develops. This occurs most often in patients with Down’s syndrome.

What causes keratoconus?

The cause of keratoconus is unknown.

Is keratoconus hereditary?

While most patients with keratoconus have no relatives suffering from the disorder, many have relatives with high astigmatism and this may be a very mild form of keratoconus. Only about one in ten patients has a relative who is suffering from keratoconus.

How is keratoconus diagnosed?

Keratoconus usually is discovered when a patient sees an ophthalmologist because of decreased vision. The diagnosis can be made through an ophthalmologist’s examination of the eye (see illustration), often involving computerized mapping of the corneal shape.

If there is a mild to moderate distortion of the cornea, contact lenses usually provide good vision. Usually these lenses are the hard or rigid type. Contact lens wear gives the cornea a smoother surface, so that the patient can see clearly.

Swelling (hydrops) in a keratoconus cornea may require treatment with eye drops.

If there is severe distortion or scarring of the cornea and contact lens wear is not possible or does not provide adequate vision, a corneal transplant is needed. A corneal transplant replaces a diseased cornea with a normal cornea from a deceased donor. (The whole eye cannot be transplanted, only the cornea.) Most people who receive corneal transplants see very clearly after the surgery. Success rates of corneal transplants in keratoconus are higher than 90%.

Can keratoconus lead to blindness?

With the proper treatment (glasses, contact lenses, or a corneal transplant), most people with keratoconus will enjoy good vision for the rest of their lives. Thanks to modern contact lenses and surgical techniques, it is rare for someone with keratoconus to be severely visually disabled.

What research is being done on keratoconus?

Vision researchers are actively studying keratoconus. At the UIC Eye Center, biochemists are trying to find the cause of keratoconus. Investigators in our Contact Lens Service are studying the effects of different contact lenses on keratoconus corneas to find the best treatments. Our corneal specialists are studying keratoconus patients and are trying to reduce the chances of graft rejection after corneal transplants.

 “Eye Facts” is an informational series and should not be used as a substitute for medical advice. For eye appointments, call (312) 996-6591. All Eye Facts illustrations and images are copyright protected and are the property of the UIC Board of Trustees. Unauthorized use of the images is prohibited. For usage of any Eye Facts content or illustrations please contact the Office of Medical Illustration at eyeweb@uic.edu or 312-996-5309 for licensing.
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