Efficient reduction of the scrolling of Descemet membrane endothelial keratoplasty grafts by engineering the medium.

The Descemet Membrane Endothelial Keratoplasty (DMEK) procedure for corneal transplantation is challenging due to the need to unscroll the donor graft within the recipient's eye. This process of unscrolling is complex, time-consuming, leads to a loss of endothelial cells and, most importantly, can negatively impact the graft's adhesion and integration with the host tissue after surgery. This problem is particularly evident when the graft is young. However, the physics behind this scrolling is not well understood, and therefore no sustainable solution is attained. Here, we propose that the concentration gradient of the medium used during transplant leads to a displacement gradient across the graft thickness, resulting in an out-of-plane folding or scrolling of the graft tissue. Using chitosan bilayer-based experimental models, it is experimentally demonstrated that this diffusion-coupled-deformation phenomenon can successfully explain why younger donor grafts tend to scroll tighter than older ones. Most importantly, we illustrate here through experiments that the medium can be engineered to reduce the scroll tightness and thus reduce the surgical inconveniences and improve post-transplant recovery. STATEMENT OF SIGNIFICANCE: This paper addresses a major issue that surgeons face while doing Descemet Membrane Endothelial Keratoplasty (DMEK) in unscrolling grafts during the graft insertion procedure. The currently used tapping method to unscroll the graft inside the patient's eye significantly reduces endothelial cell count, thus affecting its lifetime. Surprisingly, the physics behind graft scrolling is not well understood, so no sustainable solutions are proposed by the medical community. In this work, we present the underlying mechanism of DMEK graft scroll and illustrate experimentally the reason for scroll tightness through a chitosan bilayer based experiment model. Most importantly, we have successfully demonstrated that the preserving medium of the grafts can be engineered to reduce scroll tightness.