Keratoconus is a gradual change in the shape of the cornea that causes it to become cone shaped.

The condition usually begins between the ages of 15 and 25. Both eyes are usually affected, producing major changes in vision and requiring frequent changes in the prescription for eyeglasses or contact lenses. Contact lenses often correct the vision problems better than eyeglasses, but sometimes the change in corneal shape is so severe that contact lenses either cannot be worn or cannot correct vision. In severe cases, corneal transplantation (see Corneal Transplants and Why They Usually Work) may be needed.

Last full review/revision February 2003