21 Complications of Descemet Stripping Automated Endothelial Keratoplasty Over the past decade, Descemet stripping automated endothelial keratoplasty (DSAEK) has emerged as the most popular surgical alternative to full-thickness penetrating keratoplasty (PK) in the treatment of corneal endothelial dysfunction, including Fuchs endothelial dystrophy and pseudophakic bullous keratopathy.1 Because only diseased corneal tissue is targeted with the removal of host endothelium and Descemet membrane (DM) and is replaced with donor endothelium, DM, and a thin posterior stromal layer, all through a small incision, DSAEK offers patients outcomes with faster visual recovery, reduced astigmatism, and decreased risk of wound rupture.2,3 However, as with any surgical procedure, a number of intra- and postoperative complications can occur. The types of complications that can be encountered with DSAEK are oftentimes distinctly different from any complications seen after PK, and these complications can have significant visual morbidity. Careful attention to potential risk factors identified preoperatively, and understanding of methods and techniques to avoid, manage, and treat the major complications of DSAEK, will be presented herein. Despite significant variability in rates reported in the literature, donor graft detachment or dislocation into the anterior chamber is the most commonly encountered postoperative complication of DSAEK.4 Lenticles may be noted to be free floating within the anterior chamber (► Fig. 21.1), centrally detached with some residual peripheral attachment to host tissue or detachment to various degrees in the periphery. Though likely multifactorial, this phenomenon may be attributed to the presence of interface fluid that prevents the development of biochemical adhesions between donor and host stroma.4 Others have proposed that incomplete DM stripping with retained DM, intraoperative mechanical trauma to donor tissue (especially damage to donor endothelium and its pump mechanism during graft insertion or iris–cornea touch during removal of the air bubble),5 retention of viscoelastic within the interface, and even postoperative eye rubbing, may play a role. Though less well understood, postoperative intraocular pressure (IOP) variability, and particularly hypotony, have been cited as contributing to graft dehiscence.4 Fig. 21.1 Detached Descemet stripping automated endothelial keratoplasty disc free-floating in the anterior chamber and settled in the inferior angle. A number of methods and intraoperative techniques have been developed to decrease the risk of graft dislocation and to promote adhesion between donor and host tissue. Recipient peripheral stromal bed scraping (often referred to as stromal roughening) has been used successfully to create more stable and secure points of connection that not only help to prevent detachment but may even facilitate spontaneous reattachment in certain instances of dislocation.4 Corneal surface massage using a cannula tip or other instrument allows milking of residual graft interface fluid into the anterior chamber. Though not universally practiced, placement of venting incisions in the midperipheral paracentral cornea via beveled stab incisions down to the interface followed by aspiration of residual air or fluid using a 30-gauge cannula can also increase graft stability. A combination of corneal stab incisions with surface sweeping has been demonstrated by Price and Price to significantly reduce dislocation rates,6 and even further reductions may be seen using the stromal roughening technique.7,8 Although an uncommon outcome relative to the number of graft detachments, spontaneous reattachments have been documented to occur at higher rates than was previously thought, and this appears to be promoted by positioning following surgery as well as stromal scraping as already described.4 If not readily identified postoperatively on slit lamp examination, graft dislocation may be better visualized using anterior-segment optical coherence tomography (OCT)9 (► Fig. 21.2). Graft repositioning and rebubbling can be performed either at the slit lamp or under the operating microscope. It is important to attempt removal of any residual interface fluid during rebubbling, which can be performed either through corneal sweeping or aspiration of fluid via paracentral vents if present.10 Preoperative and intraoperative recognition of eyes at high risk for graft detachment (as in eyes with glaucoma filters or shunts) may prompt the surgeon to place a retention suture during surgery to facilitate rebubbling should the need arise. Whereas graft dislocation into the anterior segment remains the most common postoperative complication of DSAEK surgery, dislocation into the posterior segment is comparatively rare. In a retrospective multicenter case series, Afshari and colleagues discuss eight cases of posterior segment dislocation out of 1300 cases reviewed, of which a majority (6 of 8), occurred intraoperatively.11 They note potential risk factors as prior vitrectomy as well as aphakia or pseudophakia with a sulcus intraocular lens and open communication between the anterior and posterior segments via an open posterior capsule. As with graft dislocation to the anterior chamber, endothelial damage in cases of posterior segment dislocation is likely to occur.5,11 In fact, in the case series from Afshari and colleagues, all eyes with posteriorly dislocated lenticles required graft replacement following retrieval and removal of the damaged grafts. Fig. 21.2 Optical coherence tomography of Descemet stripping automated endothelial keratoplasty disc demonstrating central detachment and peripheral adhesion only. Aside from graft failure, other complications of posterior segment dislocation of a donor graft include cystoid macular edema, rhegmatogenous retinal detachment, and epiretinal membrane formation, which may be attributed to the modest inflammatory reaction that can develop, similar to that seen in cases of dropped nuclear fragments during cataract surgery. Given reports of tractional retinal detachment and proliferative vitreoretinopathy in cases of posteriorly dislocated grafts adherent to retinal tissue, it is advisable to attempt graft removal via pars plana vitrectomy by an experienced vitreoretinal surgeon as soon as possible.12 In cases at high risk for this complication, insertion of the donor graft via a suture pull-through method and immediate placement of a retention suture is advised. Because of the essential role played by the anterior chamber air bubble in tamponading donor graft to host stroma, the surgeon must pay close attention to its size and location at the conclusion of surgery because a large bubble in the anterior chamber or one that has drifted posterior to the iris can cause pupillary block13 (► Fig. 21.3), in turn causing closure of the iridocorneal angle in the immediate term, as well as the later development of peripheral anterior synechiae (PAS), both of which may also injure the graft endothelium and predispose to graft failure.9,10 The elevated IOP itself can also damage the endothelium. Once identified by the presence of significant postoperative pain, elevated IOP, and shallow/flat anterior chamber, pupillary block is treated by immediate partial evacuation of the air bubble using needle aspiration and replacement of the lost volume with fluid. This is often only able to be achieved by going through the iris to aspirate the air. Fig. 21.3 Pupillary block with air bubble seen posterior to the iris. This complication, however, can be avoided through a number of methods. For example, in a prospective case series of 200 patients in which none developed pupillary block, Terry and colleagues describe a technique in which an initial air bubble is placed comprising ≤ 50% of the anterior chamber after which nearly all is removed. Following this, just enough air is reinjected to cover the graft edges and, to ensure adequate mobility of the bubble, the patient’s head is moved from side to side.13 Pupillary dilation is then achieved with the placement of cyclogyl 1% and phenylephrine 2.5%. This technique did not require the use of prophylactic laser peripheral iridotomy (PI) or intraoperative iridotomy. Alternatively, a surgical PI can be placed at the conclusion of surgery. Some surgeons advocate checking patients 1 hour postoperatively to ensure that pupillary block has not occurred prior to discharge. Primary graft failure (PGF) is noted by the presence of persistent corneal edema within the first few weeks following DSAEK and is attributed to graft endothelial dysfunction (► Fig. 21.4), which may be iatrogenic or a function of the intrinsic health of the graft tissue.9,14 Endothelial trauma during graft preparation can occur, but because fewer occurrences of PGF appear to correlate with increasing surgeon experience, it is more likely that endothelial damage incurred during surgery, such as with graft insertion, manipulation, and centration, represents the primary determinant of PGF.10,13 Techniques aimed at limiting such endothelial trauma during the preparation phase include preventing artificial anterior chamber collapse during dismounting after cutting the tissue with a microkeratome9 and storing the graft with the anterior lamellar cap.15 During insertion, proper care to protect the endothelium and minimizing instrumentation contact with the graft may also decrease the rates of PGF.13 Removal of the failed graft and replacement with new tissue is the treatment when PGF occurs. Interface opacification caused by epithelial ingrowth is an uncommon complication after DSAEK surgery. It may be initially detected on slit lamp examination as a hazy lamellar surface with sharply demarcated borders in the early stage or as a homogeneous white mass at the interface in the late stage, and it can even manifest as extension to the iris surface resulting in ectropion uveae and glaucoma.16,17 The etiology of epithelial ingrowth may be due to dragging of loose host epithelial cells into the interface between the donor and host stroma during graft insertion, or migration of residual donor epithelial cells from eccentrically trephined grafts.16,18 In addition, epithelial ingrowth can also occur through venting incisions. Postoperative graft dislocation and subsequent reattachment appear to increase the risk of epithelial ingrowth.16 Moreover, host conjunctival epithelial ingrowth, in cases of retained vitreous within the surgical wound that can serve as a scaffold for migrating epithelial cells, has also been documented.16 If not in the visual axis and if not progressing, epithelial ingrowth may not always require surgical intervention. However, in cases of visual compromise from ingrowth in the visual axis, graft removal and repeat DSAEK may be necessary. Some case reports describe using intracameral 5-fluorouracil to inhibit epithelial proliferation, and, in rare instances, PK may be necessary if the epithelial ingrowth compromises not only the graft interface but the host stroma as well.16,19
21.1 Introduction
21.2 Donor Dislocation
21.2.1 Posterior Segment Dislocation of the Donor Disc
21.2.2 Pupillary Block
21.2.3 Primary Graft Failure
21.2.4 Epithelial Ingrowth
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