Endothelial keratoplasty has evolved greatly over the past 16 years: from the deep lamellar endothelial keratoplasty (DLEK) procedure of a hand-dissected donor placed in a hand-dissected bed to today’s most common procedure, Descemet’s stripping automated endothelial keratoplasty (DSAEK)—where a microkeratome donor is placed like a wart on the back side of the cornea—and on to Descemet’s membrane endothelial keratoplasty (DMEK), which replaces a diseased-stripped Descemet’s membrane with a healthy donor Descemet’s membrane.
Reasons for performing DMEK procedure
Mark A. Terry, MD, summarized three top reasons for why DMEK should be used for all routine cases of EK:
1. Visual results
2. Lower rejection rate
3. Less steroid-induced glaucoma
The primary reason to adopt DMEK is that it represents exact anatomic replacement, explained Dr. Terry, director of the Cornea Service, Devers Eye Institute, Oregon Health Sciences University, Portland, OR.
Vision results are better with DMEK than DSAEK, and the visual recovery is much faster. There is also a lower rejection rate using DMEK (<1%) compared with DSAEK (9%).
A version of DSAEK known as “ultra-thin” is sometimes thought to have vision results as good as using DMEK, but the literature shows about twice as many patients will have 20/20 vision using DMEK over ultra-thin DSAEK.1-3
Despite this, the popularity of DMEK in the United States has not increased greatly, Dr. Terry noted.
In 2016 in the United States only 6,459 cases were done using DMEK, out of 28,327 total EK cases. Part of the reason for this may be the perception that it is not easier, and not faster in the operating room.
Easier, safer with eye bank prep and stamping
DMEK has changed in the ten years since it was first introduced, Dr. Terry continued.
Standardized techniques have improved the speed of the procedure, and some of these procedures have been published.4-7
There has also been improvement in the tissue that is received from eye banks. The tissue used for DMEK is delivered pre-stripped, removing the concern of destroying the tissue in the operating room. It is pre-stamped with an “S” mark on the Descemet’s side, not the endothelial side, eliminating the problem of upside-down grafts, which can be a primary cause of graft failure. Once the tissue is inside the chamber, before the gas or air bubble is added, the “S” verifies it is right side up.
Even more recently, the DMEK donor tissue can be supplied already “pre-loaded” into a Straiko glass injector, saving time, risk, and money for the operating surgeon.
Dr. Terry noted that the Devers Eye Institute has published a standardized technique for DMEK.7
The synthesis of techniques uses pre-stripped tissue from an eye bank, which has the “S” stamp provided. The surgeon overstrips the recipient, as recommended by Kruse6, to get better adhesion in the periphery. The institute uses a Straiko glass injector (Michael Straiko, MD) and a no-bubble-tap unfolding technique developed by Edfel Yoeruek many years ago.8
José L. Güell, MD, has advocated 20% SF6 bubbles 10, which do increase adhesion in the periphery through sustained support, but air may do just as well in most cases.
It is important to note that the DMEK procedure has evolved since its beginning.
The learning curve is now very fast, Dr. Terry said. Experienced DSAEK surgeons who are turning to DMEK procedures are experiencing much better outcomes in their first cases than earlier DMEK surgeons did.3
DMEK for endothelial failure
For routine cases of endothelial failure, DMEK has a better visual outcome for the patient and lower risk of rejection, Dr. Terry explained.
Patients can stop taking steroids in just a few months, and because fewer steroids are needed, the patient can be put on fluorometholone eye drops for the time they are on steroids very quickly, to avoid steroid complications.
The learning curve is easier and faster now than ever, and the eye bank is doing the tissue preparation--making surgery faster, easier, and safer, Dr. Terry noted.
Complication rates, even in a surgeon’s early cases, can be as low as DSAEK if an established technique is used.3,7
When not to use DMEK
DSAEK is still needed for eyes with a prior vitrectomy, for tubes and traps, ACIOL, ICE and aniridia, and aphakia. DMEK can be used in those first two categories, but it is much more difficult and should probably be avoided, especially by a surgeon new to using DMEK.
The transition from DSAEK to DMEK is an additive transformation, not an exclusionary one, Dr. Terry commented.
DMEK can be done for all routine cases of endothelial replacement; DSAEK can be used for complex, high-morbidity cases, and PK is still needed for cases that need transplant for full-thickness disease.
1. Busin M, Madi S, Santorum P, Scorcia V, Beltz J. Ultrathin descemet’s stripping automated endothelial keratoplasty with the microkeratome double-pass technique: two-year outcomes. Ophthalmology. 2013;120:1186-1194.
2. Hamzaoglu EC, Straiko MD, Mayko ZM, Sáles CS, Terry MA. The first 100 eyes of standardized Descemet stripping automated endothelial keratoplasty versus standardized Descemet membrane endothelial keratoplasty. Ophthalmology. 2015;122:2193-2199. doi: 10.1016/j.ophtha.2015.07.003. Epub 2015 Aug 11.
3. Phillips PM1, Phillips LJ, Muthappan V, Maloney CM, Carver CN. An experienced DSAEK surgeon’s transition to DMEK: Outcomes comparing the last one hundred DSAEK surgeries with the first one hundred DMEK surgeries exclusively using previously published techniques. Cornea. 2017;36:275-279.
4. Dapena I, Moutsouris K, Droutsas K, Ham L, van Dijk K, Melles GR. Standardized “no-touch” technique for Descemet membrane endothelial keratoplasty. Arch Ophthalmol. 2011;129:88-94. doi: 10.1001/archophthalmol.2010.334.
5. Price MO, Giebel AW, Fairchild KM, Price FW Jr. Descemet's membrane endothelial keratoplasty: prospective multicenter study of visual and refractive outcomes and endothelial survival. Ophthalmology. 2009;116:2361-8. doi: 10.1016/j.ophtha.2009.07.010. Epub 2009 Oct 28.
6. Kruse FE, Laaser K, Cursiefen C, Heindl LM, Schlötzer-Schrehardt U, Riss S, Bachmann BO. A stepwise approach to donor preparation and insertion increases safety and outcome of Descemet membrane endothelial keratoplasty. Cornea. 2011;30:580-587.
7. Terry MA, Straiko MD, Veldman PB, Talajic JC, VanZyl C, Sales CS, Mayko ZM. Standardized DMEK Technique: Reducing complications using prestripped tissue, novel glass injector, and sulfur hexafluoride (SF6) gas. Cornea. 2015;34:845-852. doi: 10.1097/ICO.0000000000000479.
8. Yoeruek E, Bayyoud T, Hofmann J, Bartz-Schmidt KU. Novel maneuver facilitating Descemet membrane unfolding in the anterior chamber. Cornea. 2013;32:370-373.
9. Güell JL1, Morral M, Gris O, Elies D, Manero F. Bimanual technique for insertion and positioning of endothelium-Descemet membrane graft in Descemet membrane endothelial keratoplasty. Cornea. 2013;32:1521-1526.