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Standardizing the Descemet Membrane Endothelial Keratoplasty Graft Preparation Method in the Eye Bank-Experience of 527 Descemet Membrane Endothelial Keratoplasty Tissues: A Proposed Modification.

To the Editor: We commend Parekh et al1 for an excellent study and sharing their experience and providing a standardized protocol for Descemet membrane endothelial keratoplasty (DMEK) graft preparation. It has lately become widely established that DMEK graft dissection techniques are diverse and feature different strengths and weaknesses.2 The standardized protocol proposed in the study of Parekh et al1 uses application of partialthickness trephination and a cleavage hook to identify the cleavage plane and to deadhere the periphery of the graft from the underlying stroma before peeling off Descemet membrane (DM). As a referral center for endothelial transplantation in the United Kingdom, we have been performing DMEKs, predominantly selfharvesting the grafts in the operating theater immediately before the procedure. We have noticed that applying the proposed technique has indeed reduced the time needed for tissue preparation as an average in comparison with other proposed techniques.2 We have, however, been confronted with some difficulties during the deadherence of the graft periphery after performing fullor partial-thickness trephination with a guarded trephine. In several cases, DM was found to be strongly adherent to the underlying stroma, making it almost impossible to identify a cleavage plane to start DM stripping. We suspect that this is due to variation in the intermediary “Bowman-like” zone of randomly arranged collagen fibers at the DM– stroma interface, which have been shown to serve as an anchoring function between DM and posterior stroma.3,4 We have found that the procedure is facilitated using a cystotome (or other bent needle) to initially identify and separate DM from the underlying stroma and to help lift the peripheral edge of DM (Fig. 1) in an arc of 1 to 2 clock hours. Thereafter, the graft edge is lifted with forceps and further stripped with a single peel technique applying resistance to the underlying corneal button using the same cystotome (Fig. 2) and applying oscillating movements when needed (eg, tension lines with threatening tear). We agree with the authors that deep trephination cuts lead to more challenging separation of the DMEK grafts. We have noticed, however, that applying only minimal vacuum to the corneoscleral disc while mounting it on the cutting block has led to easier separation. We speculate that the vacuum and force applied by the trephine blade to the donor tissue may also compress the structures, making FIGURE 1. Cystotome used to separate the Descemet membrane graft from the underlying stroma and lift the peripheral edge.