In Corneal Transplant Procedure, Limit Loading-to-Delivery Time

Preloaded corneal grafts must be applied within 4 days to avoid endothelial cell loss and early postoperative complications, according to a study published in the American Journal of Ophthalmology. 

The retrospective clinical case series and comparative tissue preparation study looked at factors involved in the outcome of preloaded Descemet membrane endothelial keratoplasty (pl-DMEK) with endothelium-inwards. The study reviewed 55 donor tissues for ex vivo study, and 147 eyes of 147 patients indicated with Fuchs endothelial dystrophy or pseudophakic bullous keratopathy with or without cataract. 

Patients underwent standardized DMEK peeling using 9.5 mm diameter at 4 centers. That was followed by second trephination for loading the graft (8.0-9.5 mm diameter). All tissues were preloaded manually with endothelium inwards. They were preserved for 4 days or shipped for transplantation. Tissues were delivered using bi-manual pull-through technique, followed by air tamponade. A live/dead assay and immunostaining was done on ex vivo tissues. 

The main outcome measures were tissue characteristics, donor and recipient factors, re-bubbling rate, endothelial cell loss (ECL), and corrected distance visual acuity (CDVA) at 3, 6, and 12 months.

Researchers found that 4 days after surgery, significant cell loss (P =.04) was seen in pl-DMEK with loss of biomarker expression occurring in pre-stripped and pl-DMEK tissues. As a result, they recommend that graft loading to delivery time of pl-DMEK tissues in endothelium-inwards procedures “be limited to 4 days after processing.” In 40.24% of cases, rebubbling occured. At 3, 6, and 12 months, the average ECL was 45.87%, 40.98%, and 47.54%, respectively. Improvement in CDVA was significant by 3 months postoperative (0.23±0.37 logMAR) (P <.01) compared with the baseline (0.79±0.61 logMAR). Also, “a significant association (P <.05) between graft diameter, preservation time, recipient gender, gender mismatch, and recipient age to re-bubbling rate was observed,” researchers report. “Rebubbling rate and overall surgical outcomes following pre-loaded DMEK can be multi-factorial and [center] specific.”

The researchers add that several unpredictable factors appear to correlate with corneal graft detachment rate, including graft diameter, donor/recipient sex mismatch, recipient age, and center-specific criteria.

“As there are multiple factors that influence early postoperative complications, it may not be feasible for many [centers] to limit the use of available tissues,” the study explains. Therefore, the researchers support identifying the factors most suited for a specific center, such ase.g., limiting the preservation time of pl-DMEK between loading and delivering to less than 4 days after processing. This could help avoid endothelial cell loss, the loss of required proteins and, immediate postoperative complications, investigators explain. “In general, as the outcomes are [center] specific, [customizing] the donor tissue characteristics for individual recipients may be required for optimal result.”

Reference

Parekh M, Pedrotti E, Viola P, et al. Factors affecting the success rate of pre-loaded DMEK with endothelium-inwards technique: a multi-centre clinical study. Am J Ophthalmol. 2022:S0002-9394(22)00102-7. doi:10.1016/j.ajo.2022.03.009