Donor age and endothelial cell density influence the properties of Descemet’s membrane endothelial keratoplasty (DMEK) grafts, and as a result, influence the duration of the surgical procedure, according to a study published in the June 2014 Cornea.
Researchers correlated donor characteristics to the width of DMEK grafts and to the duration of graft unfolding and postoperative endothelial cell loss, to determine whether the surgical technique may be simplified by donor selection.
Two separate studies were conducted: an experimental series investigating storage and preparation of DMEK grafts, and a clinical series examining the unfolding time of DMEK grafts.
In the experimental series, 28 DMEK grafts were prepared in vitro and each graft roll width was measured. The rolls were then compared to a number of donor characteristics, including donor age, total storage time, storage deswelling time, preoperative endothelial cell count, time from death to corneoscleral excision and width of DMEK graft. Each graft was prepared in a standardized way and stored at the same temperature (34°C).
Following the experimental series of 28 graft preparations, the researchers found that both donor age and endothelial cell density had a statistically significant influence on the width of the DMEK graft (p<0.001 and p<0.05, respectively). Older donors and grafts with a higher endothelial cell count resulted in broader rolls formed spontaneously by Descemet’s membrane when placed into a buffered saline solution.
In the clinical series, 31 DMEK surgeries were performed under general anesthesia by three corneal surgeons at Albert-Ludwigs-University of Freiburg.
Researchers measured the time interval from when the graft was placed into the anterior chamber to the point when it was first attached to the posterior stroma of the host (i.e., the unfolding time). Also included in this measure is the time it takes to center the graft after it has been unfolded and before it is attached to the posterior stroma.
Donor age had a statistically significant influence on the unfolding time of the graft (p<0.01). Grafts from younger donors took longer to unfold in the anterior chamber than those of older individuals. Additionally, the investigators correlated the difference between pre-op and early post-op endothelial cell density (the latter measured a mean 104 days after surgery).
There was a statistically significant positive correlation between the relatively early postoperative endothelial cell loss and the unfolding time.
Based on the results of this study, the researchers suggest that grafts from older donors with high endothelial cell counts are the most suitable for DMEK.
Heinzelmann S, Hüther S, Böhringer D, et al. Influence of donor characteristics on descemet membrane endothelial keratoplasty. Cornea. 2014 Jun;33(6):644-8.