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Descemet Membrane Endothelial Keratoplasty—A Review

US Ophthalmic Review, 2013;6(1):29-32 DOI: http://doi.org/10.17925/USOR.2013.06.01.29

Abstract:

Descemet membrane endothelial keratoplasty (DMEK) is the most recent step forward in the evolution of endothelial keratoplasty toward thinner grafts and more natural, anatomic corneal restoration. Offering unprecedented visual results and requiring no special or expensive equipment, DMEK has the potential to become the first line treatment for corneal endothelial disorders. The surgery’s perceived shortcomings (primarily technical difficulty) have mostly been addressed by new ‘no-touch’ procedures for both graft preparation and graft unfolding in the recipient eye. And as a result, DMEK has been gaining traction with ophthalmologists the world over. Now, in its most recent formulation, DMEK is ready for the typical corneal surgeon, in any clinical setting, and at low cost.
Keywords: Descemet membrane endothelial keratoplasty (DMEK), posterior lamellar keratoplasty, corneal transplantation, endothelium, surgical technique
Disclosure: Dr Melles is a consultant for D.O.R.C. International/ Dutch Ophthalmic USA, all remaining autors have no conflicts of interest to declare.
Received: April 20, 2012 Accepted November 30, 2012
Correspondence: Gerrit RJ Melles, MD PhD, Netherlands Institute for Innovative Ocular Surgery, Rotterdam, The Netherlands E: melles@niios.com, W: www.niios.com

Introduction For almost 100 years, penetrating keratoplasty (PK) was the mainstay of therapy for patients with corneal endothelial disorders.1 That changed in 1998 with the introduction of posterior lamellar keratoplasty (PLK),2–4 later popularized in the United States as deep lamellar endothelial keratoplasty (DLEK).5–7 Selectivity was the new technique’s primary advantage. By replacing only the inner aspect of the cornea, many of the suture, astigmatism, and wound healing problems of PK disappeared. But while effective, DLEK ultimately proved too technically challenging for widespread adoption. So, the surgery was simplified, giving rise to Descemet stripping (automated) endothelial keratoplasty (DS(A)EK).8-11 And within five years, this modified technique became the global treatment of choice for corneal endothelial disorders. Still, few patients after DS(A)EK achieved best corrected visual acuities (BCVAs) exceeding 20/25. Probably, the graft’s layer of attached stroma was to blame, which thickened the cornea and seemed to undermine its optical performance.12-16 A stroma-less graft was the solution, arriving in 2006 in the form of Descemet membrane endothelial keratoplasty (DMEK).17-19 With a transplant composed solely of isolated Descemet membrane (and its endothelium), DMEK slashed graft thickness by 75 % compared to DS(A)EK, from 80 microns down to twenty. The results were dramatic: almost 80 % of patients reached ≥20/25 within six months after surgery.12,20,21 Recently, DMEK has been refined into a standardized ‘no-touch’ procedure, ready for the typical corneal surgeon in any clinical setting and at low cost.22 Compared to its predecessors (DSEK, DLEK, and their variations), DMEK provides better and faster visual recovery, usually with no additional complications. It is therefore poised to become the first-line option for corneal endothelial disorders worldwide.23 Preoperative Preparation of the DMEK Graft Ideally, DMEK grafts are prepared in an eye bank, 1–2 weeks before surgery. There, the tissue undergoes several rounds of additional screening. Principally, this consists of evaluating the cell density and morphology of the donor endothelium. Grafts which appear abnormal under the microscope—those with scarce or atypical cells, suspicious for being dysfunctional—are discarded, raising the quality of the pool of tissue for transplant. Preparing the grafts weeks in advance also adds convenience: it saves time and safeguards against unexpected tissue shortage on the day of surgery.24 On the other hand, some ophthalmologists may prefer to create the grafts themselves, in the operating room, just before surgery.25 This is especially true in the United States, where few eye banks currently supply ready-to-use DMEK tissue. Each graft takes 30 minutes to prepare, and all the steps are the same, whether in the operating room or the eye bank. The initially described DMEK graft harvesting technique consisted of stripping Descemet membrane from a corneo-scleral rim submerged in saline. This method was proven safe and reproducible, with <5 % tissue loss due to inadvertent tearing, and—surprisingly—no significant endothelial cell damage.24-28 Recently, the process was upgraded to a ‘no-touch’ procedure, making the preparation both safer and easier.29 As a bonus, the anterior portion of the corneas left over from creating the DMEK grafts (with the Descemet membrane stripped off, but otherwise intact) can be used for deep anterior lamellar keratoplasty (DALK). This added benefit applies only to DMEK, because DS(A)EK preparation – by incorporating some of the posterior stroma into the graft – mangles the corneal remains, leaving them less suitable for transplant.29-31
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  72. This figure has been published previously in Dapena et al., Arch Ophthalmol, 2011;129(1):88–94].
Keywords: Descemet membrane endothelial keratoplasty (DMEK), posterior lamellar keratoplasty, corneal transplantation, endothelium, surgical technique