Quality assurance in corneal transplants: Donor cornea assessment and oversight.

The cornea is the most frequently transplanted human tissue, and corneal transplantation represents the most successful allogeneic transplant worldwide. In order to obtain good surgical outcome and visual rehabilitation and to ensure the safety of the recipient, accurate screening of donors and donor tissues is necessary throughout the process. This mitigates the risks of transmission to the recipient, including infectious diseases and environmental contaminants, and ensures high optical and functional quality of the tissues. The process can be divided into 3 stages: (1) donor evaluation and selection before tissue harvest performed by the retrieval team, (2) tissue analysis during the storage phase conducted by the eye bank technicians after the retrieval, and, (3) tissue quality checks undertaken by the surgeons in the operating room before transplantation. Although process improvements over the years have greatly enhanced safety, quality, and outcome of the corneal transplants, a lack of standardization between centers during certain phases of the process still remains, and may impact on the quality and number of transplanted corneas. Here we detail the donor screening process for the retrieval teams, eye bank operators. and ophthalmic surgeons and examine the limitations associated with each of these stages.

Banking of corneal stromal lenticules: a risk-analysis assessment with the EuroGTP II interactive tool.

We evaluated the feasibility and performed a risk-benefit analysis of the storage and widespread distribution of stromal lenticules for clinical application using a new systematic tool (European Good Tissue and cells Practices II-EuroGTP II tool), specifically designed for assessing the risk, safety and efficacy of substances of human origin. Three types of potential tissue preparations for human stromal lenticules were evaluated: cryopreserved, dehydrated and decellularized. The tool helps to identify an overall risk score (0-2: negligible; 2-6: low; 6-22: moderate; > 22: high) and suggests risk reduction strategies. For all the three types of products, we found the level of risk to be as "moderate". A process validation, pre-clinical in vitro and in vivo evaluations and a clinical study limited to a restricted number of patients should therefore be performed in order to mitigate the risks. Our study allowed to establish critical points and steps necessary to implement a new process for safe stromal lenticule preparation by the eye banks to be used in additive keratoplasty. Moreover, it shows that the EuroGTP II tool is useful to assess and identify risk reduction strategies for introduction of new Tissue and Cellular Therapies and Products into the clinical practice.

Human Corneal Endothelial Cell Assessment From Tissues Preserved in Serum-Based and Synthetic Storage Media.

PURPOSE: To assess the difference between endothelial cells from tissues preserved in media supplemented with fetal bovine serum (FBS) and recombinant human serum albumin (rHSA). METHODS: In a donor-matched study, 48 tissues were preserved for 28 days at 31°C in Cornea Max and Cornea Syn supplemented with FBS and rHSA, respectively. Endothelial cells were visualized by 2 masked observers before and after preservation. Endothelial cell density (ECD) and the number of iatrogenic folds were counted manually. Alizarin red staining and tight junction protein (Zonula Occludens-1) were used to assess cell morphology (hexagonality and polymorphism). Intraobserver and interobserver cell counts were recorded and analyzed. Wilcoxon and one-way analysis of variance tests were used, where P < 0.05 was deemed statistically significantly different. RESULTS: Significant amount of iatrogenic folds were observed in the tissues supplemented with FBS compared with rHSA postpreservation (P = 0.0007). Approximately 69% and 71% hexagonal cells (P = 0.0303) and 29% and 26% polymorphic cells (P = 0.0234) were observed in the FBS and rHSA groups, respectively. Postpreservation, operator 1 counted 1766 cells/mm in FBS and 1864 cells/mm in rHSA. Operator 2 counted 1702 cells/mm in FBS and 1858 cells/mm in rHSA. ECD counts from FBS (interoperator) were statistically significant (P = 0.0429). However, significance was not observed in the ECD counts (interoperator) from the rHSA-preserved tissues (P = 0.8738). CONCLUSIONS: rHSA-supplemented media allow better visualization of the corneal endothelial cells. This reduces the rate of discard observed due to counting errors. Use of rHSA improves the current standard of care and reduces the use of animal-derived products.

Descemet Membrane Endothelial Keratoplasty - Complication and management of a single case for tissue preparation and graft size linked to post-op descemetorhexis disparity.

PURPOSE: To report the management of an intraoperative complication during large (9.5 mm) ultra-thin Descemet Stripping Automated Endothelial Keratoplasty (UT-DSAEK) surgery in a patient with a large area of dysfunctional endothelium. OBSERVATIONS: A single case study of an 89 y/o male with a history of Fuchs corneal endothelial dystrophy is presented. The patient was listed for a large UT-DSAEK, but due to an intraoperative complication during graft preparation, an 8.00 mm Descemet membrane endothelial keratoplasty (DMEK) was prepared from the same graft using a standardized SCUBA technique and delivered. Early postoperative examination of the graft showed decentred, residual corneal oedema in the absence of DM detachment and a well-formed anterior chamber. The endothelial graft was found attached after 3 months and the corneal oedema was cleared. After 5 months, the patient's BSCVA was recorded at 6/6(20/20) in the left eye, but complained of mild discomfort. A circular ring of corneal oedema was observed around the graft and decentralization of the transplanted graft was observed. Endothelial cell density (ECD) of the central cornea at 5th month was 1506 cells/mm2 at a focal depth of 496 µm with some polymegathism. CONCLUSIONS: and importance: It is possible to prepare DMEK starting from a failed DSAEK graft. Thickness map on corneal tomography could be a useful tool after DMEK for checking graft centration, function, and corneal recovery indirectly. It is recommended to only maintain a small distance between the descemetorhexis area and the size of the endothelial graft.