Descemet Membrane Endothelial Keratoplasty (DMEK)

Abstract

DMEK has dramatically changed the way we treat endothelial dysfunction. Every week, I perform DMEK on the second eye of multiple Fuchs' dystrophy patients after treating their first eye the week before. DMEK provides rapid visual recovery, 1 allowing rapid sequential bilateral surgery, 2 whereas when penetrating keratoplasty (PK) was the only option, bilateral transplants were typically spaced over a year apart. Current Indications The most common type of endothelial dysfunction we treat in the U.S.A. is Fuchs' dystrophy. 3 The incidence of endothelial decompensation after cataract surgery has decreased with improved phacoemulsification techniques and intraocular lenses. However, we are seeing an increase in corneal decompensation after glaucoma surgery, particularly aqueous shunts. This is a major concern, because numerous studies have shown that previous glaucoma surgery is the single biggest risk factor for endothelial keratoplasty failure. 4 The failure risk seems to be associated with the breakdown of the blood aqueous barrier and significantly altered protein levels in the anterior chamber, 5 which may create a suboptimal environment for endothelial survival. In eyes with low-grade inflammation or breakdown of the blood aqueous barrier and particularly in eyes with aqueous shunts, we should plan on potentially repeating the transplant every 4 to 5 years. Every incision leaves a scar and complicates repeat incisions in the same area. DMEK only requires a 1.8-to 2.8-mm incision, whereas Descemet stripping endothelial keratoplasty (DSEK/DSAEK) requires a 3-to 5-mm incision, and PK incisions exceed 23 mm. So DMEK is the least invasive choice for eyes at increased risk for graft failure. I currently prefer DSEK over DMEK in eyes with a large iris defect, aphakia, artificial irises, or anterior chamber lenses, because the thin DMEK tissue might fall back into the posterior chamber during unfolding and positioning maneuvers or the endothelium might be damaged by the plastic IOL or artificial iris. Eyes with extensive anterior synechia are problematic, because there is less space to position the graft. Lysing the synechia can be helpful, but they often reform. DMEK is not contra-indicated in eyes with extensive edema, but poor visualization makes it more challenging. Removing the hazy epithelium, placing air in the anterior chamber for a period of time, and staining the donor longer with trypan blue can improve visibility. Intraoperative OCT is helpful in eyes with very cloudy corneas. A hallmark of DMEK is the remarkably low risk of immunologic rejection episodes. 6 Data from prospective, randomized studies show that we can safely reduce steroid strength one month after DMEK to minimize the risk of steroid-associated intraocular pressure elevation in whites (Table 1). 7,8 African-Americans tend to have a higher risk of immunologic graft rejection, 9 so we believe it is prudent to maintain strong steroid coverage longer in patients with darker pigmentation. We prefer for our DMEK patients to keep using a weak topic...