Keratoconus is a progressive, degenerative condition in which the front of the eye (the cornea), protrudes in a cone shape causing thinning of the corneal tissue. This results in reduced and distorted vision. The condition is present from birth, but does not affect vision until the teenage years.
Keratoconus affects approximately 1 person in every 1000. The exact cause is uncertain, but a genetic link seems likely, as the incidence rate is greater if a family member has been diagnosed. Often people with keratoconus suffer from seasonal allergies and asthma, and associated rubbing of the eye can make the condition worse.