Purpose
To compare 2 lenticule insertion methods currently in use for Descemet stripping automated endothelial keratoplasty (DSAEK).
Design
Prospective randomized single-masked study.
Patients and Methods
Twenty patients with Fuchs endothelial dystrophy and pseudophakic bullous keratopathy undergoing DSAEK surgery were included and randomized to the use of either EndoGlide or EndoSerter as a delivery method for the donor lenticule. Post surgery, patients were monitored for up to 1 year. Evaluation included corrected distance visual acuity (CDVA) and refraction. Specular microscopy images were obtained at the 6- and 12-month visits. Complications, including rebubbling rate, graft dislocation, and graft failure, were recorded.
Results
Twenty eyes were randomized to receive the Tan EndoGlide or the EndoSerter injector for lenticule insertion. Mean patient age was 65.9 ± 8.4 years and 70.3 ± 9.8 years in the Tan EndoGlide and EndoSerter groups, respectively ( P = .3). Two eyes in each group needed rebubbling. The mean endothelial cell loss, including the rebubbled eyes, at the 12-month visit was 1093 ± 629 cells/mm 2 (range: 239–2109 cells/mm 2 , mean percentage cell loss 41.2%) and 877 ± 566 cells/mm 2 (range: 116–1851 cells/mm 2 , mean percentage cell loss 31.4%) in the Tan EndoGlide and EndoSerter groups, respectively ( P = .45). Mean CDVA did not show a statistically significant difference between the 2 groups at the 6- or 12-month visit.
Conclusion
The EndoSerter shows comparable results to the Tan EndoGlide. However, further investigation is warranted in order to validate these findings.
Endothelial keratoplasty has advanced dramatically since its first introduction in the early 1990s as deep lamellar endothelial keratoplasty (DLEK). Currently, Descemet membrane endothelial keratoplasty (DMEK) is gaining popularity. Despite its numerous advantages, which include a more rapid recovery, the avoidance of sophisticated and expensive machinery, and very low rejection rate, at its current stage, DMEK requires advanced surgical skills and involves a very steep learning curve. Therefore, Descemet stripping automated endothelial keratoplasty (DSAEK) is still commonly used and efforts are being made to enhance this technique. One of the most challenging surgical steps of DSAEK surgery is the insertion of the donor lenticule into the recipient’s anterior chamber with the least amount of endothelial damage possible. Although forceps delivery was shown to have equivalent safety and efficacy profile to facilitate delivery, it is considered to be a more challenging technique. For this reason different instruments have been developed to simplify lenticule insertion, and they have been shown to have variable endothelial-protective effects. The Tan EndoGlide (AngioTech, Reading, Pennsylvania, USA/Network Medical Products, North Yorkshire, UK), with a reported 12-month endothelial cell loss of 15.6%–24.6% in different studies, has addressed a few of the shortcomings of DSAEK surgery, such as endothelium-to-endothelium touch from lenticule folding and crush injury to the endothelium from mechanical compression, both of which lead to significant endothelial cell loss. Other instruments, such as the closed-chamber pulling-injection technique described by Macaluso and the Busin glide (Moria USA), offer similar properties. Recently, a new device called the EndoSerter (Ocular Systems Inc, Winston-Salem, North Carolina, USA) was introduced, and its safety and efficacy were demonstrated in a study comparing it to the previous forceps insertion technique, 6 months after DSAEK. Both of these devices, the Tan EndoGlide and the EndoSerter, enable rolling (instead of folding) of the lenticule, which reduces cell loss from endothelium-to-endothelium contact. However, the Tan EndoGlide uses specifically designed forceps to pull the tissue into the anterior chamber, usually from a nasal paracentesis, whereas the EndoSerter has a unique feature that enables self-deployment of the donor lenticule into the anterior chamber. The EndoSerter is directly connected to irrigation with balanced salt solution (BSS), which enables smooth insertion of the donor lenticule via retraction of the delivery scaffold once the inserter is fully inserted into the eye; the anterior chamber remains stable throughout the insertion process. This could hypothetically reduce endothelial cell loss even further.
In this study, we compare the safety and efficacy of the EndoSerter to that of the Tan EndoGlide in a series of 20 eyes, with a 12-month follow-up period.
Patients and Methods
This prospective comparative randomized study was approved by the institutional research ethics committee at the University Health Network, Toronto, Ontario, Canada. It is also registered as a clinical trial through the Clinical Trials Registry of the National Institutes of Health (NCT01791075), and information is publicly available ( http://www.clinicaltrials.gov ). The study included 20 eyes of 20 patients eligible for DSAEK surgery. All patients consented to participate in the study and to be randomized to receive either the Tan EndoGlide or the EndoSerter device for insertion of the donor lenticule during surgery. Patients were included in the study if they had Fuchs endothelial dystrophy and/or pseudophakic bullous keratopathy. In patients with a cataract, a combined phacoemulsification with intraocular lens implantation prior to DSAEK surgery was carried out. Patients were excluded from the study if they had a history of failed corneal transplant (penetrating or endothelial keratoplasty), peripheral anterior synechiae, vitreous loss in pseudophakic cases, or any potentially vision-limiting disease such as glaucoma, age-related macular degeneration, and diabetic retinopathy. Preoperatively, all patients underwent a complete eye examination including measurement of Snellen uncorrected distance visual acuity (UDVA), spectacle-corrected distance visual acuity (CDVA) where possible, slit-lamp examination, intraocular pressure measurement, and funduscopy. Preoperative endothelial cell count of the donor tissue was provided by the local eye bank using the Konan Keratoanalyzer EKA-98 (Konan Medical Corp, Hyogo, Japan).
Surgical Technique
Following detailed explanation of the surgery and the study objectives, all patients signed an informed consent. All surgeries were performed under neuroleptic anesthesia with sub-Tenon injection of a mixture of lidocaine hydrochloride 2% and bupivacaine hydrochloride 0.5%. In patients with a cataract, the cataract was first phacoemulsified using a 2.75-mm clear corneal temporal incision with subsequent intraocular lens implantation, followed by DSAEK surgery. The central 8.5 mm of the recipient’s Descemet membrane was stripped through a limbal incision after epithelial marking of the recipient cornea for centration purposes and after anterior chamber maintainer insertion (when necessary, with the use of the Tan EndoGlide). The donor tissue was prepared using the Moria automated lamellar therapeutic keratoplasty (ALTK; Moria SA, Antony, France) microkeratome equipped with a 300-μm head and its associated artificial anterior chamber (Moria). Following the microkeratome pass, the anterior stromal “cap” was removed and the donor tissue was marked on its stromal surface for proper positioning. We used a direct marking technique in all cases, using a gentian violet water-based marking pen to make a small, peripheral, gentle mark on the stromal side of the donor. After the tissue was transferred to a punching system, it was cut with an 8.5-mm-diameter trephine, endothelial side up. The donor lenticule was then loaded onto the respective device. A temporal limbal incision of 4.5 mm (Tan EndoGlide) or 4 mm (EndoSerter) was fashioned. In patients who had cataract surgery first, the same main incision was used for lenticule insertion after incision enlargement to the appropriate size. Two preplaced 10-0 nylon sutures enabled quick closure of the wound once the donor tissue had been inserted. In the Tan EndoGlide group, the tip of the Tan EndoGlide device was apposed against the limbal incision and Tan forceps were inserted through a nasal paracentesis to assist in grasping and pulling the tissue into the anterior chamber. In the EndoSerter group, the device was inserted into the temporal incision after removal of the blocking guard, while the deployment rings were held firmly in order to prevent pre-ejection of the graft. Following optimal positioning of the device’s tip into the wound lip, BSS irrigation was allowed through the device while it was moved forward so that the carrier edge could pass to the far end of the stripped stromal bed. The deployment wheels were moved forward while the carrier retracted in order to expose the graft until it was completely uncovered in the anterior chamber. The preplaced sutures were then closed and the tissue was apposed to the host stromal bed by injection of air into the anterior chamber. No venting incisions were applied. The eye was kept pressurized for 10 minutes. Some air was released along with BSS instillation to allow for an appropriately sized bubble in the anterior chamber. The patient was then left in the supine position for another hour in the recovery room and was instructed to stay supine for the following 24 hours after discharge.
Postsurgical Regimen and Evaluation
Postoperatively, patients were given a combination of antibiotic and corticosteroid drops (tobramycin 0.3% and dexamethasone 0.1%, Tobradex; Alcon Laboratories, Inc, Mississauga, Canada) 4 times daily for 1 month, and then switched to dexamethasone 0.1% (Maxidex; Alcon Laboratories, Inc) 4 times daily with a slow taper to once daily over 4 months. Subsequent to surgery, patients were evaluated on day 1, after 1 week, after 1 month, and then every 3 months. Evaluation included vision testing, manifest refraction, intraocular pressure measurement, and slit-lamp examination. Specular microscopy images were obtained using a noncontact specular microscope (ROBO, Konan storage system KSS 300; Konan Medical, Hyogo, Japan) at the 6-month and at the 12-month visits. Image analysis was performed using the semi-automated center technique and endothelial cell density (ECD) was recorded. Careful attention was made to include at least 100 cells in the analysis of a high-quality image unless this was not possible owing to a low cell count (usually below 1000 cells/mm 2 ). Complications, including rebubbling rate, graft dislocation, and graft failure, were recorded.
Statistical Analysis
Sample sizes for each arm were calculated for a 5% level of significance with 80% power, from a standard deviation of 250 cells/mm 2 and a minimal difference of 220 cells/mm 2 between groups, assuming that a difference of less than 5% between the groups is likely to be related to intra-observer variability during image analysis. It was determined that 10 subjects would be required in each group of the study. Differences between continuous variables were tested using the Student t test for normally distributed data (ECD and endothelial cell loss). A P value of <.05 was considered significant.
Results
Twenty eyes of 20 patients were included in the study and were randomized to have the Tan EndoGlide or the EndoSerter for lenticule insertion. Mean patient age was 68 ± 9.1 years (range, 54.6–88.4 years). Table 1 summarizes the patients’ demographic and postoperative refractive and visual acuity data for each of the tested groups. There was no statistically significant difference in mean CDVA between the 2 groups after 12 months of follow-up ( P = .29). Preoperative mean ECD did not differ statistically significantly between the 2 groups ( P = .19, Table 2 ). The mean endothelial cell loss (ECL) at the 12-month visit was 1093 ± 629 cells/mm 2 (range: 239–2109 cells/mm 2 , mean percentage cell loss of 41.2%) and 877 ± 566 cells/mm 2 (range: 116–1851 cells/mm 2 , mean percentage cell loss of 31.4%) in the Tan EndoGlide and EndoSerter groups, respectively ( P = .45, Table 2 ).
| Tan EndoGlide Group | EndoSerter Group | P Value | |
|---|---|---|---|
| Age (y), mean ± SD/range | 65.9 ± 8.4/54.6–80.4 | 70.3 ± 9.8/60.5–88.4 | .3 |
| Eye (OD/OS) | 7/3 | 9/1 | |
| Sex (M/F) | 3/7 | 5/5 | |
| 6 months post-op MRSE (D), mean ± SD/range | −0.03 ± 1.21/(−2.13)–(+1.38) | 0.93 ± 1.7/(−1.63)–(+3.88) | .2 |
| 6 months post-op CDVA (logMAR), mean ± SD/range | 0.44 ± 0.14/0.3–0.6 | 0.36 ± 0.25/0.18–0.7 | .4 |
| 12 months post-op MRSE (D), mean ± SD/range | 0.013 ± 1.17/(−2.13)–(+1.38) | 0.69 ± 1.58/(−1.5)–(+3.63) | .29 |
| 12 months post-op CDVA (logMAR), mean ± SD/range | 0.33 ± 0.12/0.18–0.54 | 0.23 ± 0.1/0.1–0.4 | .29 |
| Tan EndoGlide Group | Endoserter Group | P Value | |||
|---|---|---|---|---|---|
| Mean ± SD | Range | Mean ± SD | Range | ||
| Pre-op ECD (cells/mm 2 ) | 2654 ± 210 | 2286–2884 | 2792 ± 208 | 2451–3025 | .19 |
| 6 months post-op ECD (cells/mm 2 ) | 1630 ± 652 | 554–2370 | 1952 ± 568 | 842–2950 | .47 |
| 6 months post-op ECL (cells/mm 2 ) | 1024 ± 702 | 486–2324 | 840 ± 599 | 48–1846 | .77 |
| 6 months post-op ECL (%) | 38.6 ± 26.5 | 18.3–87.6 | 30.1 ± 21.5 | 2–66.1 | – |
| 12 months post-op ECD (cells/mm 2 ) | 1561 ± 597 | 629–2278 | 1915 ± 658 | 837–2882 | .24 |
| 12 months post-op ECL (cells/mm 2 ) | 1093 ± 629 | 239–2109 | 877 ± 566 | 116–1851 | .45 |
| 12 months post-op ECL (%) | 41.2 ± 23.7 | 9–79.5 | 31.4 ± 20.3 | 4.2–66.3 | – |
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