The Descemet membrane endothelial keratoplasty (DMEK) Rapid device is safe for the preloading and international shipping of DMEK grafts when the endothelium is outward and preserved in transport medium, and when shipping occurs within 72 hours, according to a study published in Cornea.
In an effort to validate the DMEK Rapid device for the cross-country transportation of preloaded DMEK grafts, researchers compared 2 different preservation media and graft results to determine endothelial health.
Researchers estimated the number of dead cells within the endothelium and calculated endothelial cell density. Following this initial analysis, corneas were stripped and stained with trypan blue to record the endothelial cell density, trypan blue-positive cells, and uncovered areas. Stripped DMEK tissues were then moved to a Petri dish containing either tissue culture medium or transport medium.
Investigators divided the study into 2 groups: an in-house laboratory study performed in Venice, Italy (study A), and a cross-country transportation study, where the tissues began in Venice, Italy and were shipped and analyzed at the University College London in the United Kingdom (study B).
Thirty-three tissues were collected from 26 donors (22:4 ratio of men to women). Average donor age was approximately 70 years, and average postmortem time was approximately 12.45 hours; average preservation time in the tissue culture medium was 31 days, and average endothelial cell density before peeling was 1700 cells/mm2.
Following trypan blue staining, cultures from study A (n=24) showed minimal trypan blue-positive cells before peeling in both the tissue culture medium and transport medium groups, although scattered trypan blue-positive cells were noted following peeling in each group. Investigators saw endothelial cell loss of 7.5% following peeling in the tissue culture medium group compared with 9.1% cell loss in the transport medium group.
Overall, investigators found a 20.8% (±5.2%) endothelial cell loss in the tissue culture medium group compared with the transport medium group (19.5%±6.7%).
Researchers noted small, scattered, denuded areas using Alizarin red staining (n=8) following ejection from the DMEK Rapid cartridge in both groups. Live/dead analysis via Weka segmentation showed 78.83% and 80.83% viability in each group, respectively; these differences were not statistically significant.
Due to the “slightly better viability profile” of tissues preserved in transport medium, investigators selected this medium for study B. These tissues showed “minimal mortality” of endothelial cells, in addition to maintenance of the characteristic cobblestone morphology. Uncovered areas were noted primarily in the periphery, and 1 tissue sample showed a number of rounded cells.
In total, 12.9% endothelial cell loss was noted in study B; of this loss, 12.9% was seen after stripping the tissue and 3.3% was seen after transporting the tissue to the United Kingdom. Alizarin red staining showed no uncovered areas, and maintenance of endothelial morphology without significant polymorphism. Live/dead staining demonstrated 85.16% viability.
“The DMEK Rapid device for preloaded DMEK is an easy-to-use standardized device with a limited learning curve required for eye bank technicians and surgeons,” the research concludes. “Because the tissue is rolled with endothelial outward…it can be easily taken up by the surgeons. This may also facilitate the uptake of DMEK surgeries with the use of fully validated grafts provided by the eye banks.
Wojcik G, Parekh M, Romano V, et al. Preloaded Descemet membrane endothelial keratoplasty grafts with endothelium outward: A cross-country validation study of the DMEK rapid device. Cornea. Published online September 16, 2020. doi:10.1097/ICO. 0000000000002493