Prolonged donor cornea preservation in organ culture: Long-term clinical evaluation

This thesis presents a study of the efficacy of 37 C organ culture as a method of long-term storage of human donor corneas prior to penetrating keratoplasty. Because bacterial and fungal contamination is a major biohazard using organ culture techniques, microbial studies were performed to assess this risk. Two hundred thirty nonseptic donor eyes had a contamination rate of 76.66% as they were received by the eye bank before any processing of the tissue was performed. Coagulase-negative staphylococcus and diphtheroids comprised 47.4% of all the organisms cultured from these eyes. When the anterior segment of the donor globes was immersed in gentamicin or Neosporin solution for three minutes, gentamicin sterilized 78% of the globes, whereas Neosporin sterilized only 36% of the globes, demonstrating the superiority of gentamicin decontamination of donor globes. During organ culture storage, contamination from the environment or personnel or carryover from contaminated donor eyes occurred at a rate of 0.55 contaminated organ cultures per month in spite of penicillin, gentamicin, and amphotericin B being present in the medium. Therefore, even with careful decontamination procedures of the specimen prior to organ culture, and the addition of antibiotics and antimycotics to the medium, contamination is a constant risk during the organ culture process. To reduce the risk of transplanting contaminated donor corneas, a terminal sterility procedure has been performed on all organ cultured corneas before clinical transplantation to human recipients. The initial terminal sterility check was modified after failing to detect Torulopsis glabrata contamination of the organ cultured donor cornea that resulted in endophthalmitis. In 108 transplants since modification, it has functioned satisfactorily. However, this should only be performed by well-trained microbiologists experienced in sterility check procedures. In the clinical study, 114 penetrating keratoplasties were performed by the author using donor corneas stored in organ culture an average of 16.5 days (range 2 to 35 days) prior to surgery. After a follow-up time from 6 to 63 months (average 31 months), 92 (81.8%) were successful and 22 (18.9%) failed. No cases of primary graft failure have occurred in this series. Immune rejection episodes occurred in 33 (28.9%) of the cases and accounted for the most graft failures (eight). Since this was a retrospective study, definite conclusions regarding modification of the immune graft rejection after organ culture cannot be made. However, based upon the results of this study, it appears unlikely that such modification occurs. The causes of graft failure and their frequency are similar to those reported using other storage methods. The postoperative complications seen using 37 C organ culture were similar to those reported using other storage methods, with the exception of a 9.6% incidence of wound separation using organ cultured donor corneas, as opposed to 5.6% reported using other storage methods. Technically, 37 C organ culture is a complicated and expensive method of donor cornea storage, requiring a well-trained technician as well as a microbiologic laboratory staff experienced in sterility check procedures. The major advantage of this system is the long-term storage possible with its use. Based upon the results of the investigations presented in this thesis, 37 C organ culture storage is an efficacious method of long-term donor corneal storage prior to penetrating keratoplasty and is safe when used with the appropriate personnel and safeguards.