Visual Outcomes After Descemet Membrane

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7.00 (OD) or 5.00 (OS), descemetorhexis under air was performed. Then, the Descemet roll was stained with 0.06% trypan blue dye, inserted into the anterior ...

CLINICAL SCIENCE

Visual Outcomes After Descemet Membrane Endothelial Keratoplasty Versus Descemet Stripping Automated Endothelial Keratoplasty—Comparison of Specific Matched Pairs Konstantinos Droutsas, MD,*† Apostolos Lazaridis, MD,*† Dimitrios Papaconstantinou, MD,† Dimitrios Brouzas, MD,† Marilita M. Moschos, MD,† Stephan Schulze, MD,* and Walter Sekundo, MD*

Purpose: To compare visual rehabilitation after Descemet membrane endothelial keratoplasty (DMEK) and Descemet stripping automated endothelial keratoplasty (DSAEK) for Fuchs endothelial dystrophy.

Methods: The medical records of patients undergoing endothelial keratoplasty were retrospectively evaluated. A DMEK (n = 25 eyes) and a DSAEK (n = 25 eyes) group were formed. Specific matched pairs consisting of 1 DMEK and 1 DSAEK eye with the same preoperative best spectacle-corrected visual acuity (BSCVA) were built and compared with regard to visual rehabilitation, subjective refraction, central corneal thickness, and endothelial cell density. Results: Preoperative median BSCVA (logarithm of the minimal angle of resolution) was for both groups 0.7 (range, 0.2–1.70). At 12 months, median BSCVA was 0.0 (range, 20.08 to 0.7) after DMEK and 0.3 (range, 0.1–0.52) after DSAEK (P , 0.001). The spherical equivalent changed after DMEK from 0.0 D (range, 22.75 to 4.63 D) to 0.5 D (range, 21 to 2.5 D) and after DSAEK from 20.32 D (range, 22.50 to 1 D) to 0.63 D (range, 22.38 to 2 D). Central corneal thickness decreased from 718 mm (range, 566–1041 mm) to 533 mm (range, 460–605 mm) after DMEK and from 650 mm (range, 527–749 mm) to 605 mm (range, 486–650 mm) after DSAEK. Endothelial cell density decreased from 2448 cells/mm2 (range, 2106– 3000 cells/mm2) to 1263 cells/mm2 (range, 589–2282 cells/mm2) after DMEK and from 2348 cells/mm2 (range, 2156–2781 cells/mm2) to 1327 cells/mm2 (range, 664–1972 cells/mm2) after DSAEK. Conclusions: DMEK patients showed faster rehabilitation and higher BSCVA at all postoperative visits; however, the decline in graft’s endothelial cell count and change in the spherical equivalent were similar for both procedures. Received for publication July 11, 2015; revision received January 1, 2016; accepted February 5, 2016. Published online ahead of print March 31, 2016. From the *Department of Ophthalmology, Philipps University, Marburg, Germany; and †First Department of Ophthalmology, National and Kapodistrian University of Athens, Athens, Greece. The authors have no funding or conflicts of interest to disclose. Reprints: Konstantinos Droutsas, MD, First Department of Ophthalmology, National and Kapodistrian University of Athens, Hospital G. Gennimatas, Mesogeion 154, 11527 Athens, Greece (e-mail: [email protected] yahoo.gr). Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.

Cornea  Volume 35, Number 6, June 2016

Key Words: corneal transplantation, descemet membrane endothelial keratoplasty, descemet stripping automated endothelial keratoplasty, fuchs endothelial dystrophy, visual acuity (Cornea 2016;35:765–771)

F

or over a century, penetrating keratoplasty was the gold standard of corneal transplantation. Inherent problems of penetrating keratoplasty include high astigmatism, allograft rejection, chronic endothelial cell loss, and open-sky surgery. Less invasive techniques that allow the replacement of diseased corneal endothelium were recently introduced, and thus, endothelial keratoplasty (EK) surpassed penetrating keratoplasty for the treatment of corneal endothelial pathology. Currently, the most commonly applied EK techniques are Descemet Membrane Endothelial Keratoplasty (DMEK) and Descemet Stripping Automated Endothelial Keratoplasty (DSAEK).1 In DMEK, the donor tissue comprises corneal endothelium on its basement membrane, that is, Descemet membrane (DM), and allows the selective replacement of diseased endothelium. On the other hand, the donor tissue in DSAEK contains, in addition to corneal endothelium and DM, a layer of posterior donor stroma rendering the DSAEK graft approximately 10 times thicker than DMEK.1 The almost perfect anatomical restoration achieved with DMEK is reflected in the rapid and complete visual rehabilitation as reported in several studies. In the first 100 DMEK cases published, 79% of eyes reached a best spectaclecorrected visual acuity (BSCVA) of 0.5 or better within the first month, whereas 38% reached even 1.0 or better at 6 months after surgery.2 Further studies confirmed these results.3–5 However, as the delicate DMEK graft spontaneously assumes the form of a scroll with the endothelium on its outer surface when submerged in fluid, it is more sensitive to mechanical trauma during surgery, and more elaborate maneuvers are required to achieve correct positioning onto the recipient stroma as compared with a DSAEK graft, where the endothelium lies on the inner surface of the donor disk and rigidity of the donor stroma allows easier handling.1,6,7 Hence, although DMEK has demonstrated an excellent safety profile even during the learning curve and unprecedented visual results in several case series, it is considered www.corneajrnl.com |

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Cornea  Volume 35, Number 6, June 2016

more challenging than DSAEK, which is currently the most widely adopted technique.3,6,7 Comparative studies are needed to facilitate a surgeon’s decision, as to which technique to apply as a primary treatment. Recently, a few retrospective studies comparing visual outcomes after DMEK and DSAEK were published.8–11 In 3 of these studies, comparability was given by either comparing the course of fellow eyes9–11 or matching with respect to diagnosis and donor characteristics.8 With regard to visual acuity as the primary outcome measure in the present study, we compared visual rehabilitation after DMEK versus DSAEK based on the course of pairs of eyes with identical baseline visual acuity. Hence, the matching used in the present study aims at achieving a higher level of comparability than previous studies that matched either eyes of the same patient (contralateral eye studies) or included consecutive EK surgeries.8–11

MATERIALS AND METHODS The medical records of all patients diagnosed with Fuchs endothelial dystrophy who underwent DMEK or DSAEK between February 2011 and October 2013 at the Ophthalmology Department of the Philipps University Marburg (Marburg, Germany) were reviewed. Institutional review board approval was not required because of the retrospective study method. To evaluate the potential of each surgical technique and also diminish a possible learning curve effect, only uncomplicated surgeries of otherwise healthy eyes were included in the study. Hence, we excluded patients with other ocular pathology that might influence vision potential (eg, amblyopia, macular scar, absolute glaucoma) and complicated surgeries leading to primary graft failure or repeat surgery. Finally, specific matched pairs were formed consisting of eyes with the same preoperative BSCVA, that is, each eye of the DMEK group was matched to an eye with the same preoperative BSCVA of the DSAEK group (Fig. 1). Patient’s age and sex, BSCVA, spherical equivalent, refractive cylinder, endothelial cell density (ECD), and endothelial cell loss rate were evaluated. Central corneal thickness (CCT) and thickness of the DSAEK graft were measured by Scheimpflug tomography (Pentacam; Oculus, Germany). Mean thickness of the DSAEK graft at 6 months was measured on ·5 zoomed-in Scheimpflug images. The graft thickness was measured at 5 different points (at the intersection point of the visual axis and graft and at 1 and 2 mm on both sides; Fig. 2). The average of all 5 measurements was recorded.

FIGURE 1. Flow chart showing the algorithm used to build specific pairs.

Descemet Membrane Endothelial Keratoplasty

All surgeries were performed by 2 surgeons (K.D., W.S.) using the same standardized techniques. Preoperatively, all eyes received peripheral YAG-laser iridotomy to avoid an air-induced pupillary block.

DM was stripped off from the donor corneoscleral button under sterile conditions either on the day before or immediately before surgery following the standardized technique of the Netherlands Institute for Innovative Ocular Surgery.12 Briefly, the corneoscleral button was placed with the endothelial side up on a commercially available cornea holder (DMEK holder; D.O.R.C., Germany) and stained with 0.06% trypan blue dye (Vision blue; D.O.R.C.) to improve visibility of the relevant anatomical structures. After removal of the iris root and remainders of angle structures, DM was carefully stripped off with McPherson forceps. A 9- to 9.5-mm-diameter central trephination was performed and the still attached part of central DM was stripped off from the stroma. The graft, once detached from the donor stroma, formed a roll with the endothelium on the outer surface and was kept in organ culture medium at room temperature until transplantation. For DMEK surgery, the standardized no-touch technique of the Netherlands Institute for Innovative Ocular Surgery was applied.13 After creating a 2.75-mm tunnel at the 12.00 limbus position and side ports at 1.00, 11.00, and 7.00 (OD) or 5.00 (OS), descemetorhexis under air was performed. Then, the Descemet roll was stained with 0.06% trypan blue dye, inserted into the anterior chamber with a Pasteur laboratory pipette and, after ensuring its correct orientation (endothelium facing the iris) by means of the

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Surgical Protocols

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Visual Outcomes After DMEK Versus DSAEK

FIGURE 2. Thickness of a DSAEK graft as measured on a Scheimpflug image. A, Scheimpflug image of the cornea at 6 months after DSAEK. B, Zoomed image (·5) of the same cornea. The graft thickness was measured at 5 points: At the point of intersection of the measurement’s reference axis and the graft and at 1- and 2-mm distance on both sides. The average of all 5 measurements was calculated and recorded as the mean graft thickness.

Moutsouris sign,13 the graft was unfolded by placing a small air bubble on top of the graft and moving the bubble so as to unfold the roll by applying gentle strikes on the corneal surface. Then, the air bubble was removed and another air bubble was positioned underneath the graft to press it against the recipient cornea. Patients kept a strict supine position for the following 2 hours after surgery; in case of a pupillary block or obstruction of the inferior iridotomy by the bubble, a small amount of air was released at the slit lamp.

chamber. Then the graft was placed with the endothelial side up on a silicone bank (Geuder AG, Heidelberg, Germany) and trephined with a disposable trephine blade with a diameter of 8 to 8.5 mm (Bausch & Lomb, Germany); the graft was loaded on a Busin glide (Moria SA, Mömbris, Germany) and pulled through the limbal incision with a Busin forceps (Moria SA). Incisions were sutured with Nylon 10-0, and the donor disk was pressed against the recipient stroma by filling the anterior chamber with air. Finally, removal of entrapped fluid in the interface was achieved by 4 paracentral vent incisions.

Descemet Stripping Automated Endothelial Keratoplasty

Statistical Analysis

Surgery was performed under sub-Tenon anesthesia. All DSAEK procedures were performed with the pull-through technique after Busin.14 Briefly, a 4.5-mm limbal incision was created temporally (left eyes) or nasally (right eyes) followed by 3 side ports at 1.00, 6.00, and 9.00. The recipient’s DM was removed by descemetorhexis with the anterior chamber filled with air. After removing the anterior cap of the precut donor tissue (Eye bank of the Federal State of Rhineland-Palatinate, Gutenberg University of Mainz, Mainz, Germany), the letter “F” was drawn with methylene blue on the stromal side of the DSAEK graft to allow control of its orientation in the anterior

All data were collected with Excel software (version 14; Microsoft Corp.). Descriptive and inferential data analysis was performed with SPSS software (version 16.0; SPSS, Inc.). The results are reported as central tendency and dispersion. Comparison of individual preoperative and postoperative measurements was performed with the Wilcoxon rank sum test for matched pairs, and differences of medians between the 2 groups were assessed by the Mann–Whitney U test for independent samples. A P-value less than 0.05 was considered statistically significant. For analysis of the visual acuity data, the decadic logarithm of the minimal angle of resolution (logMAR) was used.

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RESULTS Demographics All preoperative parameters were comparable between the 2 groups (P . 0.05; Mann–Whitney U test) (Table 1). The study comprised 50 pseudophakic eyes of 50 patients (25 eyes in each group). All surgeries were uneventful, and no secondary procedures such as rebubbling or repeat keratoplasty were necessary.

Best Spectacle-Corrected Visual Acuity In the DMEK group, median logMAR improved from 0.7 (range, 0.20–1.70) at baseline to 0.22 (range, 0–1) at 1 month, 0.1 (range, 20.08 to 0.52) at 3 months, 0.05 (range, 20.15 to 0.3) at 6 months, and 0.0 (range, 20.08 to 0.7) at 12 months after surgery. In the DSAEK group, median logMAR improved from 0.7 (range, 0.20–1.70) to 0.52 (range, 0.15–1.30) at 1 month, 0.40 (range, 0.15–1) at 3 months, 0.30 (range, 0.05–0.7) at 6 months, and 0.3 (range, 0.1–0.52) at 12 months after surgery (Table 1, Fig. 3). A statistically significant improvement of BSCVA was observed at 1 month after DMEK (P , 0.001, Wilcoxon rank sum test) whereas it was noted after 3 months after DSAEK (P , 0.001, Wilcoxon rank sum test).

Notably, the difference of median BSCVA between the 2 groups was statistically significant at all postoperative follow-up examinations (P , 0.001 for 1, 3, 6, and 12 months; Mann–Whitney U test) (Table 1).

Subjective Refraction The median spherical equivalent showed a hyperopic shift of 0.5 D after DMEK and 0.95 D after DSAEK. The refractive cylinder remained stable within each group and did not differ significantly between the 2 groups at all postoperative time points (Table 1).

Central Corneal Thickness Median central thickness of the DSAEK graft at 6 months was 140 mm (range, 110–190 mm). The CCT decreased from 718 mm (range, 566–1041 mm) to 533 mm (range, 460–605 mm) in the DMEK group (P , 0.001; Wilcoxon rank sum test) and from 650 mm (range, 527–749 mm) to 605 mm (range, 486–650 mm) in the DSAEK group (P = 0.068; Wilcoxon rank sum test). The cornea was significantly thinner after DMEK compared with DSAEK at 6 and 12 months after surgery (P , 0.001, Mann–Whitney U test).

TABLE 1. Median, Range, and Respective Level of Statistical Significance Achieved When Age, Visual Acuity, Refraction, Corneal Thickness, and Endothelial Cell Density Were Compared Between DMEK and DSAEK Groups; In Addition, Median and Range of DSAEK Graft Thickness Is Listed DMEK Group (n = 25) Age logMAR pre logMAR 1 mo logMAR 3 mo logMAR 6 mo logMAR 12 mo SE pre SE 3 mo SE 6 mo SE 12 mo REFcyl pre REFcyl 3 mo REFcyl 6 mo REFcyl 12 mo CCT pre CCT 6 mo CCT 12 mo ECD pre ECD 6 mo ECD 12 mo ECloss 6 mo ECloss 12 mo DSAEK graft thickness at 6 mo

DSAEK Group (n = 25)

N

Median

Minimum

Maximum

N

Median

Minimum

Maximum

P (Mann–Whitney U Test)

25 25 25 25 24 22 20 25 23 21 19 25 22 21 24 23 20 25 22 21 22 21 —

71 0.7 0.22 0.1 0.05 0 0 20.13 0.38 0.5 0.91 1.43 1.12 1 718 511 533 2448 1533 1263 39.88 44.15 —

44 0.2 0.00 20.08 20.15 20.08 22.75 22.25 21.63 21 0 0 0 0 566 448 460 2106 447 589 1.9 17.4 —

89 1.7 1 0.52 0.3 0.7 4.63 6 5.63 2.5 2.75 4 3 3 1041 601 605 3000 2402 2282 84.1 79.83 —

25 25 22 19 22 15 20 23 21 15 20 23 21 15 12 11 12 25 14 13 14 13 20

72 0.7 0.52 0.4 0.3 0.3 20.315 0.38 0.375 0.63 0.75 1 1 0.75 650 605 605 2348 1437 1327 43.4 41.5 140

58 0.2 0.15 0.15 0.05 0.1 22.5 22.25 22.38 22.38 0 0 0 0 527 505 486 2156 420 664 21 23.8 110

85 1.7 1.3 1 0.7 0.52 1 1.88 2 2 3 4 3.25 3.25 749 667 650 2781 2320 1972 81.7 72.4 190

0.93 0.92 ,0.001* ,0.001* ,0.001* ,0.001* 0.704 0.702 0.86 0.885 0.445 0.295 0.454 0.571 0.029* ,0.001* ,0.001* 0.118 0.733 0.986 0.581 0.79 —

*Statistically significant. D, diopters; ECloss, endothelial cell loss; mo, month; pre, preoperatively; REFcyl, refractive cylinder; SE, spherical equivalent.

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FIGURE 3. Chart depicting the course (x axis) of the mean decadic logarithm of the minimal angle of resolution (logMAR, y axis) in the DMEK (red line) and DSAEK groups (blue line), respectively. The vertical bars indicate the standard error. The numbers inside the graph (blue: DSAEK, red: DMEK) indicate the decimal BCVA values corresponding to the logMAR values on the y axis. The case number of each visit is given in parentheses.

Endothelial Cell Density Median ECD decreased in the DMEK group from 2448 cells/mm2 (range, 2106–3000 cells/mm2) preoperatively to 1263 cells/mm2 (range, 589–2282 cells/mm2) at 12 months after surgery. After DSAEK, ECD decreased from 2348 cells/mm2 (range, 2156–2781 cells/mm2) to 1327 cells/mm2 (range, 664–1972 cells/mm2). The median endothelial cell loss at 12 months was slightly higher in the DMEK group (44% after DMEK vs. 41% after DSAEK), but not statistically significant (P = 0.79, Mann–Whitney U test) (Table 1). Finally, no patient had preexisting glaucoma and intraocular pressure remained within normal limits during the follow-up period in all cases.

DISCUSSION

To our knowledge, this is the first comparison between DMEK and DSAEK including patients matched according to baseline BSCVA. Each of 25 pairs consisted of 1 DMEK and 1 DSAEK eye with the same preoperative BSCVA. A statistically significant improvement of BSCVA compared with preoperative values was found at 1 month after DMEK as opposed to 3 months after DSAEK. Furthermore, DMEK showed higher BSCVA values than DSAEK at all postoperative time points. At 12 months after surgery, median BSCVA [logMAR (decimal fraction)] was 0.0 (1.0) after DMEK and 0.3 (0.5) after DSAEK. Recently, several comparative studies demonstrated superior visual results of DMEK (Fig. 4). Tourtas et al8 compared the outcomes of 73 consecutive DSAEK and Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.

Visual Outcomes After DMEK Versus DSAEK

DMEK surgeries. At 6 months postoperatively, BSCVA improved from 0.7 (0.2) to 0.1 (0.8) after DMEK and from 0.75 (0.2) to 0.36 (0.5) after DSAEK. Three contralateral eye studies also compared visual outcomes after DMEK and DSAEK. Guerra et al studied 15 patients and found better BSCVA at 12 months in favor of DMEK [20/24 (0.8) vs. 20/ 32 (0.63)]. Goldich et al evaluated the course of 17 patients and found at 6 months postoperatively better BSCVA after DMEK compared with DSAEK [0.25 (0.6) vs. 0.39 (0.4)].9,10 Finally, Maier et al11 examined 10 patients and also observed higher BSCVA after DMEK compared with DSAEK [0.16 (0.8) vs. 0.45 (0.4)]. Thus, our results, based on specifically matched pairs, provide additional evidence for the superiority of DMEK in terms of visual outcomes. Moreover, all aforementioned studies, including ours, report similar levels of BSCVA, indicating that visual outcomes after EK are not likely surgeon dependent (Fig. 4). The hyperopic shift after DMEK as reported in the literature lies between 0.03 and 0.49 D,2,15–17 whereas hyperopic shift after DSAEK was between 0.71 and 1.19 D.18–20 In our series, the hyperopic shift was also smaller after DMEK (0.5 vs. 0.94 D). This observation may be explained by the negative lenticle form of the DSAEK graft, which reduces the refractive power of the cornea. In the present study, similar to published literature, the median change in absolute refractive cylinder was negligible after both DMEK and DSAEK (Table 1).2,15–18 In our series, the endothelial cell loss at 12 months was slightly higher in the DMEK group (44% vs. 41%), however without reaching statistical significance. Our findings are in concordance with those of Guerra et al and Tourtas et al who also found similar ECD values at 6 months after DMEK and DSAEK, respectively.8,17 Goldich et al10 found higher ECD levels at 6 months after DMEK (2227 6 565 vs. 1780 6 433 for DSAEK) notably with borderline statistical significance. Current evidence suggests that the optical quality of a cornea after EK seems to depend, apart from its shape and transparency, on CCT.5,16,21 Neff et al showed that BSCVA is significantly better in eyes with “thin” DSAEK grafts, that is, when the central graft thickness, as measured by anterior segment optic coherence tomography is below 130 mm.21 Recently, “ultrathin” DSAEK with a graft thickness around 80 mm with excellent visual results was described.22 In the present series, the median postoperative graft thickness, as measured manually on Scheimpflug images, was 140 mm and the majority of our DSAEK cases (18 of 25) had a thickness over 130 mm. Thus, according to the Neff categorization, our results may be applicable for standard DSAEK, but not for the “thin” or “ultrathin” versions. The superior results of DMEK can be explained by the almost perfect anatomic restoration of the recipient cornea after DMEK as opposed to a cornea after DSAEK. Thus, inherent deviations from the physiologic anatomy of a DSAEK cornea (corneal thickness, asymmetry in graft shape related to the microkeratome cut, and interface backscatter) may account for inferior visual outcomes after “standard” DSAEK. www.corneajrnl.com |

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Droutsas et al

FIGURE 4. Chart depicting results of published comparative studies reporting visual acuity (y axis) after DMEK and DSAEK (x axis). Visual acuity is presented as logMAR with the respective decadic BSCVA values given in parentheses.

However, DSAEK as a technically less challenging technique may still be indicated in (1) extremely opaque corneas where graft visibility may not be sufficient for successful DMEK surgery, (2) eyes with low visual potential (eg, macula scar, absolute glaucoma), or (3) eyes with anterior chamber intraocular lens, glaucoma tubes, or following pars plana vitrectomy, where part of the air may escape from the anterior chamber and impair graft attachment. Notably, despite the retrospective nature of the study, BSCVA (logMAR) data were almost complete in both groups except for the 12-month examination (22 DMEK vs. 15 DSAEK eyes). However, although all patients were followed up for at least 12 months, a loss to follow-up rate mainly in the DSAEK group affecting CCT and endothelial cell density data is evident (Table 1). Finally, the presented results provide further support of the current notion that DMEK offers excellent anatomic and visual rehabilitation in the treatment of eyes with Fuchs endothelial dystrophy. Despite reports emerging from different tertiary centers confirming the short and safe learning curve of DMEK2,8,10,11,15,23 and also a recently described wetlab model for DMEK training,24 graft preparation and atraumatic surgery are still considered as technically challenging.22,25 Thus, other techniques such as “thin” or “ultrathin” DSAEK have been developed, whose efficacy however still needs to be evaluated and compared with DMEK.

REFERENCES

To our knowledge, this is the first clinical comparison of visual rehabilitation after DMEK and DSAEK including pairs of eyes with exactly the same preoperative visual acuity. Our findings confirm a significantly faster and better visual rehabilitation after DMEK as compared with DSAEK in pseudophakic eyes with Fuchs endothelial dystrophy.

1. Melles GR. Posterior lamellar keratoplasty: DLEK to DSEK to DMEK. Cornea. 2006;25:879–881. 2. Droutsas K, Ham L, Dapena I, et al. Visual acuity following Descemetmembrane endothelial keratoplasty (DMEK): first 100 cases operated on for Fuchs endothelial dystrophy. Klin Monbl Augenheilkd. 2010;227: 467–477. 3. Droutsas K, Giallouros E, Melles GR, et al. Descemet membrane endothelial keratoplasty: learning curve of a single surgeon. Cornea. 2013;32:1075–1079. 4. Dirisamer M, Ham L, Dapena I, et al. Efficacy of Descemet membrane endothelial keratoplasty: clinical outcome of 200 consecutive cases after a learning curve of 25 cases. Arch Ophthalmol. 2011;129:1435– 1443. 5. van Dijk K, Droutsas K, Hou J, et al. Optical quality of the cornea after Descemet membrane endothelial keratoplasty. Am J Ophthalmol. 2014; 158:71–79. 6. Kruse FE, Laaser K, Cursiefen C, et al. 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. Endothelial keratoplasty: why aren’t we all doing Descemet membrane endothelial keratoplasty? Cornea. 2012;31:469–471. 8. Tourtas T, Laaser K, Bachmann BO, et al. Descemet membrane endothelial keratoplasty versus Descemet stripping automated endothelial keratoplasty. Am J Ophthalmol. 2012;153:1082–1090. 9. Guerra FP, Anshu A, Price MO, et al. Endothelial keratoplasty: fellow eyes comparison of Descemet stripping automated endothelial keratoplasty and Descemet membrane endothelial keratoplasty. Cornea. 2011; 30:1382–1386. 10. Goldich Y, Showail M, Avni-Zauberman N, et al. Contralateral eye comparison of Descemet membrane endothelial keratoplasty and Descemet stripping automated endothelial keratoplasty. Am J Ophthalmol. 2015;159:155–159. 11. Maier AK, Gundlach E, Gonnermann J, et al. Retrospective contralateral study comparing Descemet membrane endothelial keratoplasty with Descemet stripping automated endothelial keratoplasty. Eye (Lond). 2015;29:327–332. 12. Lie JT, Birbal R, Ham L, et al. Donor tissue preparation for Descemet membrane endothelial keratoplasty. J Cataract Refract Surg. 2008;34: 1578–1583. 13. Dapena I, Moutsouris K, Droutsas K, et al. Standardized “no-touch” technique for Descemet membrane endothelial keratoplasty. Arch Ophthalmol. 2011;129:88–94.

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CONCLUSIONS

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14. Busin M, Bhatt PR, Scorcia V. A modified technique for Descemet membrane stripping automated endothelial keratoplasty to minimize endothelial cell loss. Arch Ophthalmol. 2008;126:1133–1137. 15. Price MO, Giebel AW, Fairchild KM, et al. Descemet’s membrane endothelial keratoplasty: prospective multicenter study of visual and refractive outcomes and endothelial survival. Ophthalmology. 2009;116: 2361–2368. 16. Ham L, Dapena I, Moutsouris K, et al. Refractive change and stability after Descemet membrane endothelial keratoplasty. Effect of corneal dehydration-induced hyperopic shift on intraocular lens power calculation. J Cataract Refract Surg. 2011;37: 1455–1464. 17. Guerra FP, Anshu A, Price MO, et al. Descemet’s membrane endothelial keratoplasty: prospective study of 1-year visual outcomes, graft survival, and endothelial cell loss. Ophthalmology. 2011;118: 2368–2373. 18. Koenig SB, Covert DJ, Dupps WJ Jr, et al. Visual acuity, refractive error, and endothelial cell density six months after Descemet stripping and automated endothelial keratoplasty (DSAEK). Cornea. 2007;26: 670–674.

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Visual Outcomes After DMEK Versus DSAEK

19. Jun B, Kuo AN, Afshari NA, et al. Refractive change after Descemet stripping automated endothelial keratoplasty surgery and its correlation with graft thickness and diameter. Cornea. 2009;28:19–23. 20. Shimizu T, Yamaguchi T, Satake Y, et al. Topographic hot spot before Descemet stripping automated endothelial keratoplasty is associated with postoperative hyperopic shift. Cornea. 2015;34:257–263. 21. Neff KD, Biber JM, Holland EJ. Comparison of central corneal graft thickness to visual acuity outcomes in endothelial keratoplasty. Cornea. 2011;30:388–391. 22. Busin M, Madi S, Santorum P, et al. Ultrathin Descemet’s stripping automated endothelial keratoplasty with the microkeratome double-pass technique: two-year outcomes. Ophthalmology. 2013;120:1186–1194. 23. Dapena I, Ham L, Droutsas K, et al. Learning curve in Descemet’s membrane endothelial keratoplasty: first series of 135 consecutive cases. Ophthalmology. 2011;118:2147–2154. 24. Droutsas K, Petrak M, Melles GR, et al. A simple ex vivo model for teaching Descemet membrane endothelial keratoplasty. Acta Ophthalmol. 2014;92:e362–e365. 25. Ang M, Wilkins MR, Mehta JS, et al. Descemet membrane endothelial keratoplasty. Br J Ophthalmol. 2015. pii: bjophthalmol-2015–306837.

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