A steep and irregular curvature of the posterior surface of the cornea, usually forming a depression in the central or paracentral area. The anterior surface is normal and vision is rarely affected. The condition is typically congenital, non-progressive and unilateral, but some cases are associated with some ocular abnormalities, such as anterior polar cataract, lenticonus, ectopia lentis, iris atrophy, etc. As the cornea is much thinner it represents a contraindication to LASIK procedure. The majority of cases do not require treatment. See mesenchymal dysgenesis; video-keratoscope.