ABSTRACT
Objectives:
To evaluate the 6-month outcomes of Descemet membrane endothelial keratoplasty (DMEK) in patients with pseudophakic bullous keratopathy (PBK) and Fuchs’ endothelial dystrophy (FED) in a single center in Turkey.
Materials and Methods:
The medical records of patients who underwent DMEK were reviewed retrospectively. Best corrected visual acuity (BCVA), donor corneal endothelial cell density (ECD), donor age, duration in solution after obtaining the donor tissue, and duration after exitus of the donor were evaluated preoperatively and BCVA, ECD, and ECD loss (%) at postoperative 6 months were evaluated postoperatively. Graft detachment, graft failure, and pupillary block were recorded as surgical complications. Patients with cataract and FED underwent combined or staged procedures. Two different graft preparation techniques were utilized: 8 and 9.5 mm.
Results:
One hundred eyes of 74 patients were included in the study. Fifty-two of the eyes had FED and the remaining 48 had PBK. Mean ECD loss in 6 months was 29.2±4.4% in the FED group and 29.7±5% in the PBK group (p=0.415). Mean BCVA at 6 months was 0.06±0.05 in the patients with FED and 0.07±0.05 in the patients with PBK (p=0.378). Mean ECD loss in 6 months was 28.3±5.3% in the 8 mm group vs. 29.7±4.5% in the 9.5 mm group (p=0.255), and 28.5±5.6% in the combined group vs. 29.8±2.9% in the staged group (p=0.279).
Conclusion:
Different graft preparation techniques can be utilized with similar efficiency for DMEK surgery. A staged or combined approach can be used efficiently in the management of patients with FED and cataract. Our results are promising both for PBK and FED patients.
Introduction
After the introduction of deep lamellar endothelial keratoplasty (DLEK) in 2001 by Terry and Ousley1, a new concept evolved for patients with corneal endothelial pathologies. But the field of keratoplasty took another big step forward with the description of a new technique called Descemet’s stripping endothelial keratoplasty (DSEK) in 2004.2 Gorovoy3 modified the DSEK technique using an automated microkeratome to dissect the donor lenticule (Descemet’s stripping automated endothelial keratoplasty; [DSAEK]). Later, Melles et al.4 described the Descemet’s membrane endothelial keratoplasty (DMEK) technique, in which the surgeon can manually prepare the donor Descemet’s membrane-endothelial layer (DE) complex.
In the 2016 Eye Banking Statistical Report of the Eye Bank Association of America, the results showed that there is an increasing trend toward DMEK surgery starting from 2011, while the use of DSAEK is gradually declining.5 The results also indicate that penetrating keratoplasty has shown a declining trend relative to endothelial keratoplasty in recent years. While the most common procedure for patients with Fuchs’ endothelial dystrophy (FED) and cataract was penetrating keratoplasty in the past, endothelial keratoplasty is now the most preferred technique for surgical management according to the Eye Banking Statistical Report. However, there is no consensus about the optimal management of patients with FED and cataract. Two different approaches have been described for its management: 1) the combined technique, in which the surgeon performs endothelial keratoplasty and cataract surgery in a single session, and 2) the staged technique, in which the surgeon performs the surgeries in two different sessions. Several studies have been conducted showing no difference in the final visual acuity and endothelial cell density between these two approaches.6,7,8
Another increasing trend in the use of DMEK surgery has been observed in patients with pseudophakic bullous keratopathy (PBK). Numerous studies have been conducted to show the efficiency of DMEK surgery in this patient group.9 However, the effect of different donor preparation techniques on surgical success has not been studied.
Although several studies have presented the early and late results of DMEK surgery, no results have been reported from Turkey to date. In this study, we present the initial 6-month results of patients who underwent DMEK surgery in a single tertiary center in Turkey. We share our surgical approach for patients with FED and PBK and compare the outcomes with the current literature in terms of the endothelial cell density (ECD) and best corrected visual acuity (BCVA). In addition, we evaluated the effect of different donor preparation techniques on surgical success and compared the staged and combined techniques.
Materials and Methods
The medical records of patients who underwent DMEK for FED or PBK between 2014 and 2018 were investigated retrospectively. Patients with coexisting ocular pathology (e.g., glaucoma, uveitis) other than FED, PBK, or cataract that may interfere with BCVA and patients who had previous surgeries other than cataract surgery were excluded from the study. In addition, patients who failed to attend regular follow-ups in the first 6 months were excluded from the study (n=12). Approval from the local ethics committee was received. The study adhered to the tenets of the Declaration of Helsinki and informed consent was obtained from all patients before surgery.
BCVA, donor corneal ECD, donor age, duration in solution after obtaining the donor tissue, and duration after exitus of cadaver were evaluated preoperatively and BCVA, ECD, and ECD loss (%) at postoperative 6 months were evaluated postoperatively. Graft detachment, graft failure (development of corneal edema without any detachment), and pupillary block were recorded as surgical complications. For the patients who had cataract and FED, combined or staged procedures were performed.
ECD of the patients was evaluated with a specular microscope (Cellcheck SL Konan, Japan). Donor ECD values and other information about the donor were obtained from the Eye Bank of İstanbul University-Cerrahpaşa Cerrahpaşa Faculty of Medicine. Percentage of ECD loss was calculated as the difference between the donor ECD and ECD of the patient at postoperative 6 months. BCVA was measured using the Snellen chart, and the logarithm of the minimal angle of resolution (LogMAR) equivalent was used for statistical analysis.
Patients had complete slit-lamp examination preoperatively and at postoperative 1 day, 3-6 days, 1 month, 3 months, and 6 months, and when needed between these time points.
Results
One hundred eyes of 74 patients were included in the study. The etiology was FED in 52 eyes (52%) of 26 patients and PBK in 48 eyes (48%) of 48 patients. The mean age of the patients with FED was 67.5±5.1 years and it was 62.4±7.5 years in the patients with PBK (p=0.004). While 7 (26.9%) of 26 patients with FED were male and 19 (73.1%) were female, 28 (58.3%) of 48 patients were male and 20 (41.7%) were female in the PBK group (p=0.01). The cause of PBK was toxic anterior segment syndrome (TASS) in 4 (8.3%) of 48 eyes.
Discussion
In recent years, endothelial keratoplasty techniques (DMEK and DSAEK) have been the major surgical approach for the management of FED and PBK. Although penetrating keratoplasty is still in use, it has the disadvantages of complications, lower patient satisfaction, and lower BCVA. However, endothelial keratoplasty techniques, especially DMEK, require more surgical experience. Despite this drawback, after enough surgeries, it can be performed in any center because special surgical equipment is not necessary for this surgical approach, unlike DSAEK. In DMEK, the surgeon has the advantage of preferring the best approach for the patient in each step of donor tissue preparation. Furthermore, in a recent meta-analysis, DMEK was found to show better postoperative results regarding BCVA, patient satisfaction, and graft-related issues.10 In this study, we presented our results of the increasingly popular DMEK surgery in 100 eyes with FED or PBK.
In clinical studies, the success of DMEK surgery is usually evaluated based on both ECD loss and change in BCVA. While Droutsas et al.11 showed 31.6% ECD loss at 6 months after DMEK surgery for the treatment of patients with FED, Ham et al.12 showed 28.4% ECD loss. Consistent with these previous studies, we observed mean ECD loss at 6 months of 29.2±4.4% in the FED group and 29.7±5% in the PBK group. Our study also showed that there was no difference between the FED and PBK patients in terms of ECD loss at 6 months. This indicates that DMEK surgery might be equally successful in terms of ECD in patients with FED and PBK.
In general practice, the 9.5 mm technique is preferred for donor graft preparation.13 In our study, we evaluated whether there is a difference between the 9.5 mm and 8 mm techniques. Although contact with the endothelial layer during the 8 mm preparation technique might cause concern about increased ECD loss, we did not observe any significant increase in loss. Our results showed that both techniques can be used effectively with comparable endothelial cell loss.
Although penetrating keratoplasty was the main approach in the past, recent advances in endothelial keratoplasty techniques have made it the main approach for patients with FED. However, there is controversy regarding the best approach to patients with FED and cataract. This issue is important because the rate of cataract formation within 1 year after any endothelial keratoplasty was reported to be as high as 40%.14 Two different approaches have been described in the literature. In the combined technique, the surgeon can perform the DMEK surgery together with phacoemulsification in the same session, whereas in the staged technique, DMEK is performed in another session after phacoemulsification. Previous studies offered conflicting results about the success of both approaches. Most of the studies suggested that the two techniques were similar in terms of final BCVA and ECD.6,7 Schoenberg et al.8 reported the results of 108 triple DMEK procedures and found that triple DMEK safely achieved excellent BCVA. Sykakis et al.6 reported increased graft dislocation rate in the combined technique. However, this increase was attributed to the use of Healon-GV rather than Healon. Similar to the previous studies, we did not observe any difference between the techniques in terms of ECD loss or BCVA at 6 months in our study.
Graft failure is one of the complications of DMEK surgery. Re-DMEK, back-up DSEK, or penetrating keratoplasty can be used for the management of graft failure.15 Heinzelmann et al.16 showed that pre-cut donor graft was linked to increased graft failure rate. Thus, donor tissue preparation should be performed immediately before surgery. In our study, graft failure was observed in 10 eyes (10%) and an additional DMEK procedure was performed for all of these cases. TASS was the cause of PBK in 4 of these cases. Penetrating keratoplasty was needed in 5 of these cases. Although previously we showed that DSAEK was successful in cases of chronic TASS in terms of visual and anatomical outcomes,17 our study suggests that DMEK might not be a good approach for patients with PBK secondary to TASS. However, further studies with a larger number of patients should be conducted to compare the success of DMEK and DSAEK for the treatment of PBK secondary to TASS.
Another complication of the DMEK surgery is graft detachment. This complication can be managed with re-bubbling. Although the rates of total and partial graft detachment were 30% and 62-63% in initial reports,18,19,20,21,22 the detachment rate decreased to as low as 4-34.6% in recent years due to increased surgical experience.19 In our study, 3 eyes (3%) with partial graft detachment and 1 eye (1%) with total graft detachment were observed and air was applied to the anterior chamber to provide reattachment. Suspecting upside down graft application, we performed re-DMEK in the patient with total graft detachment.
Study Limitations
The relatively short follow-up time, small number of patients with PBK secondary to TASS, and the retrospective, non-randomized, and descriptive design of the study are limitations of our study. Due to the non-randomized and descriptive nature of the study, some of our findings may lack generalizability. In addition, central corneal thickness data were not included in the study.
Çalışmanın Kısıtlılıkları
İzlem süresinin göreceli olarak kısa olması, TASS’ye sekonder PBK’si olan hastaların sayısının az olması, çalışmanın retrospektif, randomize olmayan ve deskriptif tasarımı çalışmamızın kısıtlılıklarıdır. Çalışmamızın randomize olmayan ve betimsel doğasından ötürü, bazı bulgularımız genellenemeyebilir. Ayrıca, merkezi kornea kalınlığı verisi çalışmaya dahil edilmemiştir.
Conclusion
DMEK was found to be a safe and effective method for patients with FED and PBK. In patients with FED together with cataract, we did not observe any difference in final BCVA or ECD between the staged or combined procedures, which indicates that both approaches can be used efficiently in these patients. Furthermore, no difference in 6-month ECD was found between graft preparation using the 8 mm or 9.5 mm techniques. Further studies including central corneal thickness data should be performed to investigate the results of the increasingly popular DMEK procedure.
