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Keratoconus is a degenerative disorder in which the CORNEA thins, allowing it to protrude from the surface of the EYE in somewhat of a cone shape. Keratoconus affects both eyes though often progresses at different rates in each eye. Ophthalmologists do not know what causes keratoconus, though it appears to run in families. Keratoconus is painless though results in progressive VISION IMPAIRMENT, typically in the forms of MYOPIA (nearsightedness) and ASTIGMATISM (distortions of vision resulting from the irregular surface of the cornea). As these REFRACTIVE ERRORS are the primary symptoms, the keratoconus may not become apparent until the coning becomes obvious.
Treatment for mild to moderate keratoconus is rigid gas-permeable contact lenses, which correct the refractive errors of vision as well as help contain the shape of the cornea. As the keratoconus progresses, however, contact lenses become less effective, and the thinned cornea may not be able to tolerate them. Keratoconus ultimately destroys the cornea and is a leading reason for CORNEAL TRANSPLANTATION, which replaces the diseased cornea with a donor cornea. Corneal transplantation successfully restores vision in about 90 percent of people who have keratoconus and undergo the procedure.
In 2004 the US Food and Drug Administration (FDA) approved a new treatment for keratoconus, corneal inserts, which are tiny plastic rings the ophthalmologist implants along the edge of the cornea. The corneal inserts flatten the cornea, reducing the coning. Corneal inserts come in different thicknesses to allow less or more flattening and are replaceable.