THE EFFECT OF THE PLASTIC VERSUS GLASS STAINING VESSEL DURING DMEK GRAFT PREPARATION ON THE RATE OF ENDOTHELIAL CELL LOSS

Endothelial cell loss (ECL) during corneal graft preparation affects graft survival and the re-grafting rates. During Descemet membrane endothelial keratoplasty (DMEK) donor tissue is incubated in Trypan blue ophthalmic solution, typically in either a glass or plastic vessel. DMEK grafts are exquisitely sensitive, with ECL documented from any form of touch. Furthermore, cellular damage of cells due to oxidative stress and mitochondrial depolarization secondary to exposure to micro-plastic chemicals has been established in the literature. This study aimed to investigate how the material in contact with DMEK tissue during staining impacts the rate of ECL to better inform surgeons and material scientists when choosing materials for DMEK.

This study was conducted at Hôpital Maisonneuve-Rosemont (HMR) and the Jewish General Hospital (JGH), Montréal, Canada. This study was approved by the CIUSSS-EMTL and the JGH Ethics Boards.

Data were collected from all patients who underwent DMEK surgery by the same surgeon (Dr.J. Choremis) between January 2019 and June 2020 at two sites. Patients operated at JGH constituted the plastic group whereas patients operated at HMR were the glass group. Patients with ocular co-morbidities and patients who passed away within 6 months of surgery were excluded from all analyses. The primary endpoints were the rate of ECL, absolute ECL, and percentage ECL, at 12-30 months. The secondary endpoints were re-bubbling and graft failure rates, at ≥6 months. ECL was the difference between pre and post-operative specular microscopy counts. The unpaired student’s t-test, chi-squared test, and ANCOVA were used with a power of 0.8 and a significance of 0.05.

The results demonstrate that there is a significant difference between plastic and glass groups in the rate of ECL at 12-30 months post-DMEK, with a smaller rate of loss in the plastic group (2.49% vs. 3.37% ECL/month, p=0.010). Future data beyond 30 months will help determine if these differences have clinically meaningful effect for patients and the need for re-grafting. There were no significant differences in the other endpoints and no confounding variables. In addition, there were no significant differences between the rates of re-bubbling or of graft failure at 6-30 months.

These data demonstrate that the choice of material used as a staining vessel for DMEK has a significant impact on the rate of ECL. This has practical implications for the choice of vessel and the development of new technologies for DMEK surgeries. With further investigation, confirmation of the superiority or, with targeted samples, the non-inferiority of plastic will have substantial impact on DMEK materials development. Of note, the target sample size was not met therefore the power of these conclusions may be reduced. Nevertheless, these data support further investigation into the effect of synthetic materials on ECL in order to optimize surgical procedures leading to a successful DMEK surgery.