"Keratoconus Keratoconus (also known as ""conical cornea"") is a degenerative disease of the eyes that manifests itself as a gradual degradation of the cornea into a more conical form than the typical eyeball.  This condition can cause extreme nighttime vision distortion, sensitivity to light, itching, ""ghost"" images and some distortion of daytime vision. The etiology of this condition is not fully understood, though it's known that proteases break down many of the keratin bonds in Bowman's layer of the cornea, causing a relaxation of the tissues.  In most patients with keratocornea, the degradation will ""settle"" at a degree that can be corrected by glasses. In 25% of patients, however, corneal transplant may be called for, in order to allow nighttime vision and increased sight during the day. Diseases of the Eye: Number One. Moorfields Manchester Institute of Ophthalmology, The Medical Illustration Department, pre-1950."