A case of keratoconus of a 19-year-old girl was reported by the authors. In the left eye acute ectasia showing an opacification and swelling of the corneal tissue and subsequent corneal scars was noted. In the right eye there was mild affection of the cornea with ectasia. Partial penetrating keratoplasty of 6mm diameter was performed on the left eye with success. The graft survived well and retained its transparency. The vision improved from counting fingers to 0.9 (corrected) 4 months after the operation. A contact lens was worn in the fellow eye (OD). The vision improved to 1.0 from 0.06 (0.8×-3.0 D. (The symbol is abbreviated)-4.0 D. Cyl. × 70°). The diseased corneal tissues removed during the keratoplasty was subjected to a histological study. It revealed changes typical for keratoconus. There were ruptures of the Bowman's membrane. These ruptures were fulfilled with fibrous tissues.