Definition of Keratoconus:

Keratoconus is degeneration of the structure of the cornea. The cornea is the clear tissue covering the front of the eye.

The shape of the cornea slowly changes from the normal round shape to a cone shape.

Causes, incidence, and risk factors:

The cause is unknown, but the tendency to develop keratoconus is probably present from birth. Keratoconus is thought to involve a defect in collagen, the tissue that makes up most of the cornea.

Some researchers believe that allergy and eye rubbing may play a role.

Also, there is an association between keratoconus and Down syndrome.