Histopathologic changes after thermokeratoplasty for keratoconus.

Six patients had penetrating keratoplasty following thermokeratoplasty (TKP) at different time intervals. The standard temperature used was between 90 degree and 95 degree C. with constant saline irrigation. The corneal buttons were studied by light and electron microscopy. Immediate changes observed included epithelial necrosis, marked degneration of keratocytes, and endothelial edema. After 24 hours, evidence of acute inflammation was noted in the subeptihelial zone and superficial stroma, and the endothelial changes persisted. One month after TKP, there was evidence of cellular regeneration of all the corneal layers. Eight months later, regeneration of the endothelial cells, keratocytes, and epithelium was present. Regeneration of the epithelial basement membrane was defective.