The corneal endothelium is responsible for preserving corneal transparency by maintaining a dynamic equilibrium of corneal stromal hydration. Corneal Endothelial Cells (CECs) health is approximated by evaluating the Endothelial Cell Density (ECD) of corneal tissues though specular biomicroscopy. ECD is a key determinant of long-term tissue survival after corneal transplantation, as corneal graft function is directly dependent on the number of viable CECs. However, ECD represents only an estimation of total corneal endothelial health and is a suboptimal proxy for future endothelial failure.~In the current chain of supply of donor corneal tissues, no independent evaluation of endothelial cell viability by the surgical team tasked with transplanting the donor corneal tissue is anticipated. We have previously shown a poor correlation between ECD declared by the eye bank providing the tissue and tissue quality as assessed independently by a cornea surgeon performing the transplantation (unpublished data).~In this study, we describe a simple method to independently evaluate the overall endothelial viability of donor corneal tissue which can be adopted both by eye banks before shipment and by the corneal surgeons before transplantation in the operating theatre. This method uses basic image analysis to assess the extent of endothelial cell death and/or denuded endothelial areas with the use of Trypan Blue, a vital dye commonly employed during corneal transplantation. Endothelial cell loss is visualized and quantified as Trypan Blue Positive Areas (TBPA).~The primary objective of this study is to quantify the extent of TBPA in the operating theatre before corneal transplantation. Secondary objectives include the assessment of the correlation of TBPA with declared ECD and CECs mortality, as well as the longitudinal analysis of endothelial cell loss as a function of time from surgery and initial TBPA over a follow-up of 12 months.
The purpose of this international cohort study is to validate a new method for intraoperative assessment of endothelial viability in donor corneal tissues for transplantation, and to correlate endothelial health as assessed by the surgical team to functional and structural long-term outcomes in the cohort of patients receiving them.