Endotoxin in storage medium of human corneal grafts and clinical course after penetrating normal-risk keratoplasty.

Purpose: It is well known that endotoxins in storage medium may stimulate cytokine production and expression of adhesion molecules as well as endothelial damage in human corneal grafts. It has been supposed that endotoxin exposure of corneal grafts may, therefore, cause immune reactions and lead to reduced endothelial cell count after penetrating keratoplasty. It was the purpose of this prospective study to evaluate if this hypothesis is true.

Methods: A consecutive series of 274 samples of sterile organ culture storage medium from 274 human corneal grafts was collected between August 1998 and February 1999 and tested for endotoxin using Limulus amebocyte-lysate assay (LAL) after 7 days of organ culture. Threshold endotoxin level was set at 1.0 U/ml. A total of 161 grafts were transplanted and 113 were discarded. Within the 161 corneas transplanted, 62 were grafted to normal-risk patients and 99 to high-risk patients. Only normal-risk keratoplasty patients were included in the study and followed for at least 10 months. Immune reactions, graft failures, and postoperative endothelial cell counts were recorded.

Results: The mean endotoxin level in organ culture medium of all transplanted grafts was 1.07+/-2.96. Mean endotoxin level in organ culture medium of discarded grafts was 1.68+/-5.76, with 71 samples being below and 42 above the threshold of 1.0 U/ml called endotoxin-negative and endotoxin-positive, respectively. In all 36 culture medium samples from the 62 grafts transplanted to the group of normal-risk keratoplasty patients were endotoxin-negative and 26 endotoxin-positive. An influence of endotoxin levels on incidence of immune reactions, graft failure, and postoperative endothelial cell counts could not be revealed in patients with normal-risk keratoplasty.

Conclusion: Low endotoxin levels in storage medium neither seem to promote immune reactions nor to contribute to postoperative chronic endothelial cell loss in normal-risk keratoplasty patients.