Descemet membrane endothelial keratoplasty (DMEK) has been gaining popularity for the treatment of endothelial diseases as studies have shown it provides better visual outcomes than Descemet-stripping automated endothelial keratoplasty (DSAEK).1,2 However, the surgical technique is more challenging, and success largely depends on optimum control of anatomy of the anterior chamber, iris–lens diaphragm, and vitreous.3
Descemet membrane endothelial keratoplasty in aphakic eyes with accompanying iris defects complicates unfolding the graft and sustaining an efficient air tamponade and raises the potential risk for posterior dislocation of the air and the graft itself. The absence of vitreous support accentuates these problems, causing recurrent globe collapse during intraoperative maneuvers.4 Hence, it is still unclear whether DMEK is feasible in eyes with complicated anterior and posterior segment situations.
We report a challenging case of an aphakic vitrectomized eye with a large iris defect in which DMEK was technically possible and successful when special precautions were taken.
A 58-year-old man was referred to our clinic with endothelial decompensation in the right eye after having combined vitrectomy and scleral-fixated intraocular lens (IOL) implantation following blunt trauma. He had a history of scleritis in both eyes 15 years ago, which resulted in extensive scleral thinning. The corrected distance visual acuity (CDVA) in the right eye was counting fingers at 2 m. Examination showed bullous keratopathy, 3 clock hours of iris defect, and limbal stem cell deficiency with 360-degrees of superficial and stromal vascularization (Figure 1). The central corneal thickness (CCT) was 1000 μm (epithelial thickness 60 μm; stromal thickness 940 μm) (Figure 2). Descemet membrane endothelial keratoplasty was planned.
Donor tissue was harvested from a 61-year-old man within 6 hours postmortem, and the corneoscleral button was stored in organ culture medium. After evaluation of endothelial cell morphology and viability, Descemet membrane was stripped from the posterior stroma with the endothelium side up and trephined to obtain a 8.5 mm diameter graft. Visualization was improved by scraping the thickened epithelium at the beginning of the surgery, and descemetorhexis was initiated under air. At this stage, a 23-gauge pars plana infusion cannula was inserted at the inferotemporal quadrant 3.0 mm from the limbus. Infusion fluid was used to increase vitreous pressure and maintain anterior chamber stability. After descemetorhexis, a sutureless scleral-fixated 3-piece IOL was observed to be subluxated and removed. Surgery was continued in the now aphakic vitrectomized eye without the support of iris in the superior quadrants. The prepared donor graft was stained with trypan blue 0.1% and was loaded into a glass pipette (DORC International BV) in a double-scroll configuration. An endoilluminator was used to maintain correct orientation of the graft roll while in the pipette. The graft was then injected into the anterior chamber over the relatively intact inferior part of the iris tissue. Infusion was turned on and off as needed to preserve the positive pressure of the vitreous cavity and to keep the anterior chamber shallow. A series of tapping techniques was used to initiate unfolding of the graft. After the initial unfolding, a small air bubble was injected underneath the graft and corneal tapping continued. With the help of the infusion pressure lifting the air bubble, the graft was stabilized between the air and the recipient stroma, which facilitated further unfolding of the graft by tapping maneuvers. The air bubble was gradually enlarged in proportion to the opening of the peripheral edges of the DMEK roll to avoid folding the tissue again. This maneuver provided complete unfolding of the DMEK roll at the stromal surface in the absence of iris–lens support. When the graft appeared well centered, the infusion pressure was increased to push the air bubble and to tamponade the completely unfolded graft against the recipient stroma (Figure 3) (Video 1, available at http://jcrsjournal.org). Some of the air was aspirated at the end, and sulfur hexafluoride 20.0% was injected into the anterior chamber. The patient was instructed to remain supine for 24 hours.
The next day, the gas bubble migrated to the posterior segment; however, the graft remained properly positioned and no re-bubbling was required at the follow-up. Three months postoperatively, the patient's CDVA improved to 20/200 and the CCT decreased to 712 μm. The conjunctivalized epithelium was 74 μm thick; however, the stromal thickness had decreased to 638 μm and there was no evidence of interface between the donor and recipient tissue (Figure 2).
Descemet membrane endothelial keratoplasty in an aphakic vitrectomized eye presents several challenges that necessitate special precautions. First, recurrent globe collapse and deepening of the anterior chamber can occur in the absence of posterior support by the vitreous and complicate graft unfolding. In addition, lack of vitreous counterpressure might cause fluctuations in the position of the iris–lens diaphragm, and the air bubble in the anterior chamber may push the iris–lens diaphragm backward instead of tamponading the graft against the recipient stroma, thereby resulting in donor detachment.
Yoeruek et al.4 reported a high rate of complications in a group of 20 vitrectomized eyes that had DMEK. These complications consisted of repeated globe collapse with recurling of the graft during surgery and postoperative graft detachment.
Several authors have suggested the use of a pars plana infusion to stabilize the posterior segment. Titiyal et al.5 described the use of pars plana infusion to perform DSAEK in an aphakic vitrectomized eye. The infusion fluid in the vitrectomized eye helped overcome globe collapse, posterior dislocation of the donor disc, and escape of air tamponade. Sorkin et al.6 used a similar technique to perform DMEK in a series of 12 vitrectomized eyes, which provided safe graft delivery and handling.
Aphakia is another concern that might warrant modification of the technique. There is a risk for posterior dislocation of the graft through the pupil with the loss of intracameral air in aphakic eyes, which was previously reported in several cases of DSAEK.7 Because DMEK grafts are thinner than DSAEK grafts, the risk for graft dislocation is higher. The presence of an accompanying iris defect raises a further concern. To avoid the complication of graft dislocation, a staged approach with initial formation of the iris–lens diaphragm and secondary DMEK has been suggested in aniridic or aphakic eyes.3 However, the subluxated IOL had to be removed in our case, and scleral or iris fixation was not possible because of extensive scleral thinning and the iris defect. In this case, regulation of the eye pressure with infusion allowed proper unfolding and attachment of the graft. When the graft was injected into the anterior chamber and during the initial unfolding, it stayed afloat in the infusion current. Here, it is also important to have a sufficient amount of iris tissue to help hold the graft in place. The iris defect was limited to 3 clock hours in this case, and the remaining part of the iris provided enough support. After initial unfolding by tapping, a small air bubble was introduced underneath the graft. The positive pressure created by the infusion fluid helped levitate this air bubble and the graft toward the recipient stroma. Thereby, the graft could be unfolded at the stromal surface without using the iris–lens diaphragm. Gradually, increased air effectively tamponaded and attached the graft to the stroma with the help of infusion pressure. The gas tamponade that was left at the end of surgery escaped through the pupil on the first postoperative day; however, this did not result in graft dislocation at the follow-up.
Although there are technical difficulties, considering the accompanying limbal stem cell deficiency and severe neovascularization in our case, we believe that DMEK is the most appropriate approach, offering lower rejection rates than conventional keratoplasty and DSAEK.8
In conclusion, this report shows the feasibility of DMEK in complicated cases, such as eyes with aphakia, a defective iris, or vitrectomized globes. The use of pars plana infusion and unfolding the graft at the stromal surface appears to be helpful in these cases.
Neither author has a financial or proprietary interest in any material or method mentioned.
Goldich Y, Showail M, Avni-Zauberman N, Perez M, Ulate R, Elbaz U, Rootman DS. Contralateral eye comparison of Descemet membrane endothelial keratoplasty and Descemet stripping automated endothelial keratoplasty. Am J Ophthalmol 2015; 159:155-159. Available at: http://www.ajo.com/article/S0002-9394(14)00657-6/pdf
. Accessed November 16, 2017
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