Pathology of late endothelial failure: late endothelial failure of penetrating keratoplasty: study with light and electron microscopy.
PURPOSE: Late endothelial failure of penetrating keratoplasty can be defined as gradual decompensation (increasing thickness with loss of clarity) of a previously clear graft without apparent cause. This study examined the possibility that a chronic subclinical rejection process may be occurring in grafts that fail from late endothelial failure. METHOD: Six patients fulfilling the diagnostic criteria for late endothelial failure who underwent repeated keratoplasty were studied. The clinical course and results of specular microscopy were reviewed. The failed corneal graft for each patient was examined by light and electron microscopy. RESULTS: Sequential specular microscopy demonstrated low initial postoperative endothelial cell density with continued decrease in density and increase in corneal thickness over the first 5 postoperative years. Electron microscopy revealed irregular-shaped cells of varying size with many abnormal features, lying on abnormal Descemet's membrane. Degenerating endothelial cells were commonly seen. There was no sign of acute or chronic inflammation. CONCLUSIONS: The pathologic findings are suggestive of an unstable and highly stressed endothelial cell population in late endothelial failure but are nonspecific. There was no evidence of acute or chronic rejection at the time of graft failure.