TECHNIQUES Simulation Model for DMEK Donor Preparation Vikas Mittal, MS, Ruchi Mittal, MS, Swati Singh, MS, Purvasha Narang, MS, and Priti Sridhar, DOpt Purpose: To demonstrate a simulation model for donor preparation in Descemet membrane endothelial keratoplasty (DMEK). Methods: The inner transparent membrane of the onion (Allium cepa) was used as a simulation model for human Descemet membrane (DM). Surgical video (see Video, Supplemental Digital Content 1, http://links.lww.com/ICO/A663) demonstrating all the steps was recorded. Results: This model closely simulates human DM and helps DMEK surgeons learn the nuances of DM donor preparation steps with ease. The technique is repeatable, and the model is cost- effective. Conclusions: The described simulation model can assist surgeons and eye bank technicians to learn steps in donor preparation in DMEK. Key Words: DMEK, wet-laboratory model, endothelial keratoplasty (Cornea 2018;0:1–3) D escemet membrane endothelial keratoplasty (DMEK) is increasingly becoming the procedure of choice for corneal endothelial dysfunctions such as pseudophakic bullous keratopathy and Fuchs endothelial dystrophy. 1 This surgery involves selectively replacing diseased Descemet membrane (DM) with healthy DM from the donor cornea. Although excellent results have been reported with DMEK, technical difficulties limit its widespread use by corneal surgeons. 1,2 We describe a unique simulation technique to develop reflexes required for donor preparation in DMEK, which we encoun- tered while conducting DMEK training courses. SIMULATION MODEL The inner transparent membrane of the onion closely simulates human DM. Surgical steps are detailed below (see Video, Supplemental Digital Content 1, http://links.lww.com/ ICO/A663). 1. An individual thick fleshy onion layer (OL) is peeled off. An 18- to 25-mm wide circular section is prepared using either a knife or trephine. 2. This OL is placed on a stable surface or Teflon block with the concave side facing upward (Fig. 1A). This will simulate the corneoscleral button. 3. An 8-mm trephine is used to make an impression in the center of the OL. One should be careful to avoid full-thickness punching. Only superficial layers are being cut with minimum pressure (Fig. 1B). This will simulate the initial marking of DM. 4. Trypan blue dye (0.4%) is used to stain the impression to delineate the transparent membrane (Fig. 1C). 5. A Sinskey hook or curved tying forceps is used to create a ledge between the inner membrane and the underlying fleshy part all around. While performing this step, the OL is stabilized between the index finger and the thumb. The membrane should be submerged in the fluid (Ringer lactate/balanced salt solution) throughout the procedure to simulate the real situation. 6. After a ledge is created, trypan blue dye is injected once again between the membrane and the underlying fleshy part (Fig. 1D). This step simulates staining of the stromal side of DM that will help in its identifi- cation throughout the procedure. 7. The membrane is then gently peeled using curved tying forceps until two thirds of the membrane gets separated from the underlying stroma. The direction of the ap- plied force should be toward the opposite end of the membrane (similar to DM harvesting in which the force is directed toward the opposite limbus). While peeling, one should keep looking at the edge of the membrane for any tears. If any adhesion is encountered, the force vector should be changed to a circumferential one. 8. After two thirds of the membrane has been separated, it is kept lying on the other side. The separated area is dried using a cotton bud or surgical sponge before stamping (Fig. 1E). 9. The membrane is then repositioned using the fluid. Once unfolded, the peripheral folds are settled using a surgical sponge along the edge of the membrane. This step is quite similar to DM stripping in DMEK, with the only difference being that the membrane of the OL gets curled away from its stroma, whereas DM curls toward the corneal stroma. It is slightly chal- lenging to keep the membrane in place (compared with human DM) because of its thickness. This step is important to avoid any folds while flipping the corneoscleral button in DMEK for stamping. Received for publication January 23, 2018; revision received February 18, 2018; accepted February 21, 2018. From the LJ Eye Institute, Ambala City, Haryana, India. The authors have no funding or conflicts of interest to disclose. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.corneajrnl.com). Correspondence: Vikas Mittal, MS, LJ Eye Institute, Model Town, Ambala City, Haryana 134002, India (e-mail: vikas_mittal@hotmail.com). Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved. Cornea  Volume 0, Number 0, Month 2018 www.corneajrnl.com | 1 Copyright Ó 2018 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.