Author Affiliations: Netherlands Institute for Innovative Ocular Surgery; and Melles Cornea Clinic (Drs Liarakos, Dapena, Ham, and Melles, and Ms van Dijk); Amnitrans EyeBank Rotterdam (Dr Melles), Rotterdam, the Netherlands; and Naval Hospital, Athens, Greece (Dr Liarakos).
Objective To define various Descemet graft unfolding techniques in Descemet membrane endothelial keratoplasty.
Methods In a retrospective analysis, the surgical videos of 100 consecutive Descemet membrane endothelial keratoplasty cases with at least 6 months of follow-up were evaluated and categorized. The Descemet graft unfolding methods were categorized into 4 basic techniques and 3 auxiliary techniques.
Results All Descemet membrane endothelial keratoplasty surgical procedures could be completed using (a combination of) 4 Descemet graft unfolding techniques: (1) standardized no-touch graft unfolding using a double roll, (2) carpet unrolling while fixating 1 graft edge (Dirisamer technique), (3) small air bubble–assisted unrolling (Dapena maneuver), (4) the single sliding cannula maneuver. Additional maneuvers included turning over the graft when oriented upside down (flushing); manual graft centration with a cannula; and bubble bumping to unfold peripheral inward folds. In 73% of surgical procedures, technique 1 was used, while a combination of techniques was used in 44% and auxiliary techniques in 62%. None of the techniques showed a correlation with the best-corrected visual acuity, endothelial cell density, or postoperative complication rate (P > .10).
Conclusions Descemet membrane endothelial keratoplasty may be further facilitated by using controlled techniques for unfolding the Descemet graft inside the recipient anterior chamber, either as stand-alone techniques or used in various combinations.
Recently, we described a technique for selective replacement of the Descemet membrane (DM), referred to as DM endothelial keratoplasty (EK), for the management of corneal endothelial disorders.1,2 Although visual outcomes after DMEK may surpass those of earlier endothelial keratoplasty techniques such as Descemet-stripping (automated) endothelial keratoplasty (DSEK/DSAEK),3- 5 concerns have been raised about the feasibility of DMEK, in particular unfolding the Descemet graft within the anterior chamber of the recipient eye.6 For that reason, we standardized the procedure as a no-touch surgical technique7 to enable corneal surgeons to begin DMEK with a relatively short learning curve.3,8
Although the standardized no-touch DMEK technique may be used in most cases, the orientation and configuration of the Descemet graft may vary after its injection into the recipient's anterior chamber. For example, its orientation may be upside down when rotation of the graft occurs during injection, while tightness and/or the shape of the graft may primarily depend on intrinsic tissue characteristics such as elasticity, diameter, donor, and age. Furthermore, alternative Descemet graft unfolding techniques may be preferred with a less forgiving anatomy of the recipient anterior chamber (eg, in phakic eyes or eyes with a small or shallow anterior chamber, in aphakic eyes, or after posterior segment surgery) or in the presence of nonanatomical structures such as an anterior chamber intraocular lens or a glaucoma tube.
Therefore, the purpose of this study was to identify and categorize various intraocular Descemet graft unfolding techniques in a series of 100 consecutive DMEK surgical procedures to describe different approaches and evaluate how these techniques correlated with the eventual clinical outcome and/or the incidence of postoperative complications.
From a larger group of 350 DMEK cases, the surgical videos of 105 consecutive cases (surgical procedures 196-300) were selected because the most recent surgical procedures were considered the most informative about the current techniques used to unfold the Descemet graft inside the recipient anterior chamber. These cases also provided sufficient postoperative follow-up time (≥6 months). All videos were retrospectively analyzed; 5 cases were excluded, 3 because of low vision potential (eg, age-related macular degeneration, amblyopia, and optic neuropathy), 1 case had a DMEK failure and underwent a DSEK 1 month after the initial DMEK, and 1 case was lost to follow-up.
Hence, the study included a total of 100 DMEK surgical procedures performed for Fuchs endothelial dystrophy (89%), pseudophakic bullous keratopathy (5%), failed primary DSEK or DMEK (3%), congenital glaucoma (2%), or posttraumatic corneal decompensation (1%). Of the 100 patients, 39 were men and 61 were women; 28% had phakic eyes and 72% had pseudophakic eyes. Surgical procedures were performed and/or supervised by 2 experienced surgeons (I.D. and G.M.). The average (SD) patient age was 66.2 (12.9) years. All patients signed an institutional review board–approved informed consent form; the study was conducted according to the Declaration of Helsinki (clinicaltrials.gov Identifier: NCT00521898).
From donor globes obtained less than 24 hours post mortem, corneoscleral buttons were excised and stored by organ culture in modified minimum essential medium at 31°C.4,9 After 1 week of culture, endothelial cell morphology and viability were evaluated, and the corneoscleral buttons were mounted endothelial side up on a custom-made holder with a suction cup. The Descemet membrane was stripped off from the posterior stroma, so that a 9.5-mm diameter flap of posterior DM with its endothelial monolayer was obtained.10- 12 The Descemet roll, which formed spontaneously with the endothelium at the outer side, was then stored free floating in organ-culture medium until the time of transplantation (ie, after another 5-10 days).
In recipient eyes, a 9-mm diameter epithelial mark was made to outline the area of DM excision. A 3-mm tunnel incision was made just within the limbus, entering the anterior chamber just at the mark. With an inverted Sinskey hook (DORC International BV) and/or Descemet scraper (DORC International BV), a circular portion of DM was scored and stripped from the posterior stroma under a complete air fill of the anterior chamber, so that a 9-mm diameter descemetorhexis was created, and the central portion of DM was removed from the eye.13
The donor Descemet roll was thoroughly rinsed and stained with a 0.06% trypan blue solution (VisionBlue; DORC International BV) and sucked into a custom-made injector (DORC International BV).1,4,7 Using the injector, the donor Descemet roll was inserted into the anterior chamber and the graft was oriented endothelial side down (donor DM facing recipient posterior stroma) by careful, indirect manipulation of the tissue with air and fluid and positioned onto the recipient posterior stroma.1,4,7 The anterior chamber was completely filled with air for 60 minutes, followed by an air-liquid exchange to pressurize the eye. Each surgical procedure was recorded on DVD (Pioneer DVR-RT601H-S).
Postoperatively, the patients were evaluated at 1 day; 1 week; and 1, 3, and 6 months after the surgery. Donor endothelial cell density was evaluated in vitro (Axiovert 40 inverted light microscope; Zeiss) and photographed (PixeLINK PL-A662; Zeiss).10 In patient eyes, endothelial cell density (ECD) was evaluated in vivo with the noncontact specular microscope (Topcon SP3000P; Topcon Europe Medical BV). Images of the central corneal window were manually corrected and 3 measurements were averaged. Best-corrected visual acuity (BCVA), ECD, as well as intraoperative and postoperative complications were recorded in a MySQL database.
Surgical videos were retrospectively analyzed by a blinded observer (V.L., corneal fellow) for the maneuvers used to unfold the graft. The Descemet graft unfolding process was defined by the time interval from the moment of graft insertion into the host anterior chamber until the final positioning of the graft onto the recipient posterior stroma. All intraoperative manipulations were categorized in specific basic techniques and auxiliary maneuvers, and the duration of the unfolding process was timed.
Statistical analysis was performed with SPSS version 15 for Windows (SPSS Inc). Because a different combination of 2 or more techniques was used in most surgical procedures, regression analysis was conducted for correlations between the various Descemet graft unfolding techniques and clinical outcome in terms of BCVA and ECD loss at 6 months as well as the complication rates. The relative impact, if any, of each technique on the final outcome was measured. Analysis of variance was used to assess differences, if any, between the techniques, and the t test was used to compare stand-alone with combined techniques. Statistical significance was determined as P ≤ .05.
By reviewing the surgical videos of a total of 100 consecutive DMEK surgical procedures, 4 separate graft unfolding techniques and 3 auxiliary techniques could be distinguished (Figure 1 and Figure 2; Table), which are described here in more detail. All techniques allowed for complete unfolding of the Descemet graft without any physical touch, except for the step of graft centration, which sometimes required direct physical manipulation.
Figure 1. Decision tree describing the use of the 4 basic Descemet graft unfolding techniques (techniques 1-4) and the 3 auxiliary techniques.
Figure 2. Diagram displaying the use of the basic Descemet graft unfolding techniques (techniques 1-4) in 100 consecutive Descemet membrane endothelial keratoplasty (DMEK) surgical procedures, either as a stand-alone technique or combined with 1 or 2 other techniques.
A video demonstrating the different intraocular graft unfolding techniques in DMEK is available online (http://www.youtube.com/watch?v=T2lAh_gKNiA; for related videos, also search for keywords DMEK and NIIOS).
In 73% of cases (73/100), our previously described standardized no-touch DMEK technique7 was used either as a stand-alone technique (38% of cases, 38/100) or in combination with another technique (35% of cases, 35/100) (technique 1; Figure 2 and Figure 3; Table). The most essential step in this technique was performed before implantation: in a glass vial the Descemet roll was manipulated by irrigation with balanced salt solution (BSS) until the graft was opened and folded back while forming 2 adjacent rolls, a so-called double Descemet roll. If implanted with the opening between the 2 flaps facing the recipient cornea (ie, with the hinge facing down, as can be visualized using the Moutsouris sign; Figure 4),7 a first separation of the rolls (ie, the upward folds) could be achieved by gentle taps onto the outer cornea, after which the graft was unfolded by positioning and enlarging an air bubble between the 2 rolls on top of the graft. After completely unfolding the Descemet graft over the iris, the air was removed from the interface and, with the same cannula, air was then injected underneath the Descemet graft to position the tissue onto the host posterior stroma.
Figure 3. Intraoperative images of technique 1, the standardized no-touch Descemet membrane endothelial keratoplasty technique: unfolding a double Descemet roll. A, After injecting a double Descemet roll into the host anterior chamber, with both curls pointing upward (ie, a positive Moutsouris sign), gentle taps applied onto the outer recipient cornea with a cannula are used to start unfolding the graft. B, A small air bubble is positioned on top of the donor tissue to secure the Descemet graft in its upright orientation and to allow for centration of the graft by vibrating movements with the cannula onto the outer corneal surface. C, By enlarging the air bubble, the graft is fixated onto the iris while its peripheral edges are completely unfolded. D, The air is then aspirated from the interface between the Descemet graft and the cornea and injected underneath the Descemet graft to secure the transplant onto the host posterior stroma by leaving the anterior chamber completely filled with air for 1 hour. Throughout the unfolding process, direct physical contact between the graft and any instrument is carefully avoided.
Figure 4. Artist impression displaying the double Descemet roll and the Moutsouris sign. When the Descemet graft is oriented correctly within the anterior chamber (curls of the double roll facing upward), the tip of the cannula can be positioned inside a peripheral curl so that the tip appears blue because of the overlying blue-colored donor tissue (Moutsouris sign positive) (A and B). When the graft is positioned upside down (edges facing downward), the tip of the cannula does not find the curls so the tip will not change in color (Moutsouris sign negative) (C and D).
If no double Descemet roll could be obtained before implantation, or if the double roll fell back into a single roll after implantation, 1 of the following alternative unfolding techniques was used.
When the Descemet roll was tight, no double roll could sometimes be obtained or the double roll fell back into a single roll or asymmetric double roll (with just a small flange bordering the larger body of the Descemet roll). In these cases (22%; 22/100), the Dirisamer technique was used (Figure 2 and Figure 5; Table). By applying gentle force on its outer surface with a cannula, the host cornea was pressed against the iris, stabilizing the already unfolded peripheral flange of the Descemet graft. By applying gentle taps with a parallel second cannula over the adjacent larger body of the Descemet roll, the tissue could be unfolded like unrolling a carpet. When most of the tissue was unfolded, centration and positioning of the Descemet graft was commonly finalized using another technique in 15% of cases (15/100).
Figure 5. Intraoperative images of technique 2 (Dirisamer technique) : using 2 cannulas to unfold a single Descemet roll. A, After injection, if the donor tissue falls back into a single Descemet roll, the outer curl of the roll can often be separated from its larger body by gently tapping onto the outer corneal surface. B, Once the outer curl falls back onto the iris, it may be fixated by gentle pressure with 1 cannula onto the outer corneal surface. Meanwhile, gentle strokes are applied parallel to the remainder of the Descemet roll with a secondary cannula (C and D).
In 43% of cases (43/100), the Dapena maneuver was used to start unfolding the graft. Meanwhile, in 35% of cases (35/100), it was used in combination with 1 of the techniques previously described (Figure 2 and Figure 6; Table). In this technique, a small air bubble was positioned on top of the partially unfolded graft, and while manipulating the air bubble with a cannula at the outer surface of the host cornea, the Descemet graft was unfolded by using the air as a intraocular tool to unroll the flanges of the graft from the inside.
Figure 6. Intraoperative images of technique 3 (Dapena maneuver): unfolding the Descemet roll using a small air bubble. When techniques 1 and 2 fail or are considered less preferable (eg, in phakic eyes or eyes with a shallow anterior chamber), a small air bubble may be positioned on top of the graft, which is unfolded by manipulating the air bubble from the outer corneal surface with a cannula (A-D).
In 14% of cases (14/100), the Descemet roll showed a latent tendency to unfold by itself, commonly referred to as a loose Descemet roll, so that the graft could be largely unfolded by using a single sliding cannula maneuver (Figure 2 and Figure 7; Table). In this technique, gentle repetitive downward movements were applied on the outer corneal surface with a cannula, while sliding the cannula parallel to the Descemet rolls toward the periphery. In 4 cases (4%), complete Descemet graft unfolding could be achieved, but in the remaining 10 cases (10%), another technique was required to finalize the unfolding process.
Figure 7. Intraoperative images of technique 4, the single sliding cannula maneuver to unfold a loose Descemet graft. A, After injecting a double Descemet roll in the host anterior chamber (with both curls pointing upward [ie, a positive Moutsouris sign]), the graft already shows a tendency to unroll by itself. After draining the side port to shallow the anterior chamber, the Descemet graft is unrolled by downward strokes with a cannula over the outer corneal surface, parallel to the body of the Descemet roll (B-D).
Auxiliary techniques included maneuvers that could be combined in specific situations with the standardized technique or any other technique just described.
If the Moutsouris sign was found to be negative (ie, the Descemet graft was oriented upside down after insertion in the anterior chamber), gentle flushing with BSS through 1 of the side ports was performed to turn the graft over in 30% of cases.
Centration of the Descemet graft was commonly achieved by applying small vibrations onto the outer corneal surface so that the tissue could freely move across the anterior chamber, while the graft was stabilized with a small air bubble on top of it. If the anatomy of the anterior chamber did not permit repositioning the Descemet graft, the tissue was centered using a 30G cannula or Sinskey hook at the very edge of the graft to manually pull the tissue into position, as performed in 47% of cases.
Once the larger area of the Descemet graft was unfolded, small inward folds (with the endothelium facing the host posterior stroma) may persist. Bubble bumping (ie, gentle taps onto the outer corneal surface overlying the inward folds) were applied to completely unfold the graft in 36% of cases.
In 44% of the surgical procedures (44/100), a combination of techniques was used. For example, unrolling the Descemet graft may be initiated by using 2 cannulas to unfold a single Descemet roll (technique 2), while the procedure may be finalized by unfolding the Descemet roll using a small air bubble (technique 3) (Figures 1, and 2, and Figure 8; Table).
Figure 8. Intraoperative images of a combination of techniques 2 and 3 (ie, using 2 cannulas to unfold the single Descemet roll [Dirisamer technique]) and unfolding the Descemet roll by using a small air bubble (Dapena maneuver). With experience, any combination of the 4 basic Descemet graft unfolding techniques may be used to unfold the graft more quickly and with minimal manipulation. For example, the Descemet graft unfolding process may be started by using 2 cannulas to unroll the graft (Dirisamer technique) (A and B). Meanwhile, the process is completed using indirect manipulation with a small air bubble (Dapena maneuver) (C and D).
None of the 4 basic or auxiliary unfolding techniques, or any combination of these techniques, showed a correlation with the BCVA, ECD, or the postoperative complication rate at 6 months (all P > .10); however, the number of eyes in some of the groups was rather small. In cases with a tight Descemet roll, the use of 2 cannulas (technique 2) was preferred over the other unfolding techniques. The surgical time for unfolding and positioning the Descemet graft was on average (SD) 17.9 (10.5) minutes for all surgical procedures (N = 100). For surgical procedures in which only a single unfolding technique had been used (n = 55), the surgical time was on average (SD) 16.8 (9.2) minutes. For surgical procedures with a combination of techniques (n = 45), the surgical time was on average (SD) 19.2 (11.8) minutes. No difference in surgical time was found among the 4 unfolding techniques, but prolonged BSS flushing required to turn over Descemet grafts initially oriented upside down, correlated with longer intraoperative time (P < .001). Prolonged BSS flushing did not affect the BCVA and/or ECD at 6 months (P > .10).
At 6 months after DMEK surgery, 84% of eyes reached a BCVA (SD) of 20/40 (≥0.5) or greater and 64% reached 20/25 (≥0.8) or greater. Preoperative donor ECD was on average (SD) 2530 (207) cells/mm2 and declined to 1547 (537) cells/mm2 (P < .001) (Table).
In recent years, the concept of endothelial keratoplasty has been refined to DMEK (ie, the transplantation of an isolated donor Descemet membrane carrying its endothelium) for the treatment of Fuchs endothelial dystrophy and other types of endothelial dysfunction. Advantages of DMEK over penetrating keratoplasty and the earlier endothelial keratoplasty techniques, such as DSEK/DSAEK, include better visual outcomes because thinner grafts allow for better visual performance of the transplanted cornea14,15 and more efficient use of donor corneal tissue.16,17 With standardized no-touch DMEK, about 80% of cases can now reach a BCVA (SD) of 20/25 (≥0.8) or greater at 6 months after surgery, with about 50% reaching 20/20 (≥1.0) or greater. Given these outcomes, the technical feasibility of DMEK may be the main drawback for surgeons to convert to DMEK as a preferred treatment method.3,4,18,19
Owing to the worldwide adoption of DSEK/DSAEK, most surgeons may yet be familiar with performing a descemetorhexis (ie, the removal of the diseased, central Descemet membrane), approximately 9-mm diameter from the recipient posterior stroma. Therefore, in our study, we focused on the second part of a DMEK surgery by analyzing the implantation and unfolding of the donor Descemet graft in more detail. For this purpose, we reviewed the surgical videos of 100 consecutive DMEK procedures to define distinctive graft unfolding methods, which could be categorized into 4 basic techniques and 3 auxiliary maneuvers.
When starting out with DMEK, we implanted the Descemet graft as a single roll into the recipient anterior chamber, before partially unfolding the graft by irrigation, and positioning a small air bubble underneath the donor tissue to lift it toward the recipient posterior stroma. Although feasible, this approach allowed for limited control in unfolding, centering, and positioning the Descemet graft. To overcome this problem, we manipulated the Descemet graft into a double roll in a glass vial on the surgical table (Figure 4).7 The double Descemet roll can then be loaded in an injector and, after checking its upward orientation, injected into the recipient anterior chamber. Inside the eye, the upright orientation of the Descemet graft can again be confirmed by the Moutsouris sign (Figure 4).7 Then, although it will initially be perceived as counterintuitive, the Descemet graft is unfolded by positioning an air bubble on top of the Descemet graft, in between the 2 curls pointing upward, to center and flatten the entire graft over this iris. Thereafter, the air can be removed from the interface and then injected underneath the Descemet graft to lift the yet unfolded tissue onto the recipient posterior stroma.7
Therefore, obtaining a correctly oriented double Descemet roll in the recipient anterior chamber may be the most essential step in facilitating further unfolding of a Descemet graft because it allows for continuation in a standardized fashion (ie, to complete the surgery as a no-touch DMEK procedure), as previously described.7 In the current study, a double Descemet roll could be obtained in 73% of cases, so that we adopted the formation of a double Descemet roll as a first basic technique in unfolding the Descemet graft (technique 1; Figures 1-3; Table). However, in 35% of cases, this approach was combined with other manipulations to unfold the graft. Furthermore, in an additional 27% of cases, alternative techniques were primarily used because a double Descemet roll could not be obtained, most often because the Descemet graft was either too loose or too tight.
If too loose, the donor Descemet appeared to lack sufficient elasticity to maintain a configuration as a double roll. Inside the recipient anterior chamber, the donor tissue showed a tendency to unfold by itself, which can be facilitated by gently moving a cannula over the outer surface of the recipient cornea, the so-called single sliding cannula technique (technique 4; Figure 7; Table). Once unfolded over the iris, the Descemet graft could be easily lifted onto the recipient posterior stroma by positioning an air bubble underneath the graft.
More challenging was a Descemet roll that was too tight (ie, tissue with too much elasticity to maintain a double roll). These cases could virtually always be managed by applying gentle taps onto the recipient outer corneal surface, through which the Descemet roll was loosened until an outer curl falls back onto the iris. Once obtained, the outer curl could then be sandwiched between the cornea and the iris by applying downward pressure with a cannula (technique 2; Figure 5; Table) or by positioning a small air bubble on top of the curl (technique 3; Figure 6; Table). With experience, all of these techniques could readily be used in any combination considered most suitable for the actual surgical situation (Figure 8; Table).
In addition, 3 auxiliary maneuvers were identified to handle specific situations. When the Descemet graft is oriented upside down (Figure 4), irrigating/flushing against the upper or lower part of the graft was used to turn over the donor tissue. Although the Descemet graft could commonly be centered through manipulation from the outside, manual centration with an air cannula at the very edge was sometimes required. Although it has been reported that grafts exceeding 8 mm in diameter are more difficult to handle,6 a 9.5-mm Descemet graft is often self-centering because of its relatively large diameter. Small inward folds at the peripheral edge were carefully redressed by bubble bumping (ie, gentle taps on top of the cornea over such folds), creating a small current of fluid that unfolds the edge of the graft, because such an inward fold tends to spring away from the host cornea after surgery, causing a partial graft detachment.
In conclusion, with the 4 techniques just described, all of the DMEK surgical procedures could be completed. Within the studied group, none of the techniques showed any correlation with the visual acuity and ECD at 6 months, and/or the incidence of postoperative complications, indicating that choosing the most effective unfolding technique during surgery is justified because the preferred technique or combination of techniques in any given eye may not affect the final clinical outcome.
Correspondence: Gerrit R. J. Melles, MD, PhD, Netherlands Institute for Innovative Ocular Surgery, Rotterdam, the Netherlands (firstname.lastname@example.org).
Submitted for Publication: April 9, 2012; final revision received April 30, 2012; accepted May 2, 2012.
Published Online: September 10, 2012. doi:10.1001/2013.jamaophthalmol.4
Author Contributions: Dr Melles had full access to all data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Financial Disclosure: Dr Melles is a consultant for DORC International BV/Dutch Ophthalmic USA.
Funding/Support: Dr Liarakos received the 2011 Annual Scholarship from the Hellenic Society of Intraocular Implants and Refractive Surgery.
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