BASIC INVESTIGATION
Evaluation of a New Technique for Preparation of Endothelial Grafts for Descemet Membrane Endothelial Keratoplasty Ashley Brissette, MD,* Ronan Conlon, MD,† Joshua C Teichman, MD, MPH, FRCSC,† Season Yeung, MBBS, FRANZCO,† Setareh Ziai, MD, FRCSC,† and Kashif Baig, MD, MBA, FRCSC†
Purpose: The purpose of this study was to compare the Muraine technique, a relatively new method for preparing endothelial grafts for Descemet membrane endothelial keratoplasty (DMEK), with the current standard submerged cornea using backgrounds away (SCUBA) peeling technique.
Methods: This study was a prospective ex vivo investigation. In a wet-lab setting, 20 donor corneas were prepared for DMEK using The Muraine technique and 20 donor corneas using the SCUBA technique. In each of the technique groups, 10 corneas were prepared by a corneal surgeon and 10 were prepared by a corneal fellow. Primary outcome measures were the time needed to prepare endothelial grafts and the number of graft tears.
Results: In the SCUBA technique, median time to prepare grafts was shorter for both the surgeon (301 6 85 seconds) and fellow (523 6 58 seconds) compared with the Muraine technique (surgeon, 359 6 83 seconds; fellow, 543 6 44 seconds). However, these findings were not statistically significant (surgeon, P = 0.33; fellow, P = 0.24; pooled, P = 0.46). There was a statistically significant difference between surgeon time and fellow time for each technique (SCUBA technique, P = 0.0005; Muraine technique, P = 0.002). In the Muraine technique, there were 5 graft tears (surgeon = 2, fellow = 3), and no graft tears in the SCUBA technique, which was statistically significant (P = 0.047). Conclusions: The present study demonstrates that the SCUBA technique may be a more effective technique to prepare endothelial donor grafts for DMEK. Key Words: Descemet membrane endothelial keratoplasty, Muraine technique, submerged cornea using backgrounds away, transplant technique, donor graft (Cornea 2015;34:557–559)
Received for publication September 12, 2014; revision received January 2, 2015; accepted January 11, 2015. Published online ahead of print March 6, 2015. From the *Department of Ophthalmology, Queen’s University, Kingston, ON, Canada; and †University of Ottawa Eye Institute, Ottawa, ON, Canada. The authors have no funding or conflicts of interest to disclose. Reprints: Kashif Baig, MD, MBA, FRCSC, University of Ottawa Eye Institute, 501 Smyth Rd, Suite W6223, Ottawa, ON K1H 8L6, Canada (e-mail: [email protected]). Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Cornea Volume 34, Number 5, May 2015
T
he best possible visual outcome in posterior corneal disease requiring transplantation relies on selective transplantation of only Descemet membrane (DM) and endothelium, producing an anatomically pure replacement of what is removed. One of the first described techniques for preparing posterior corneal grafts was deep lamellar endothelial keratoplasty (DLEK), which was then refined to Descemet stripping (automated) endothelial keratoplasty (DSEK/ DSAEK).1–4 Further selective transplantation of only DM and endothelial layers led to the development of Descemet membrane endothelial keratoplasty (DMEK).5 DMEK has the advantage of being minimally invasive and offers more rapid visual recovery than penetrating keratoplasty.6–8 Studies have shown less graft rejection with DMEK, and it also has the advantage of leading to more predictable refractive outcomes after transplantation by eliminating donor stromal thickness and contour.7,9,10 A critical step in DMEK surgery is preparing donor DM to minimize trauma because the delicate DM is prone to tears and endothelial cell loss.11 Proper donor tissue harvesting techniques are essential to maximize preservation of donor endothelial cell density (ECD) to secure long-term graft survival and reduce the loss of precious donor tissue.12 An effective and reproducible donor graft harvesting technique is required, and modifications of techniques are frequently published.7,11,13,14 A recent report outlined a new method for preparing endothelial grafts for DMEK, the Muraine technique.15 The Muraine Punch (Moria, Antony, France) and an artificial anterior chamber are used for this procedure. The authors of the report demonstrated that both histologic and electron microscopic sections confirmed the cleavage between DM and posterior stroma on the corneas used for research. Also, there was minimal change to ECDs before and after dissection using the Muraine technique. Clinically, the authors reported ECDs of 2656 6 28 cells per square millimeter (range, 2450–3100 cells/mm2) preoperatively and 1658 6 43 cells per square millimeter (range, 900–2600 cells/ mm2) 6 months postoperatively.15 Thus, the authors concluded that the Muraine technique was a reliable technique for preparing DM grafts. Recently, a study by Stoeger et al evaluated the ECDs after the Muraine technique (using partial trephination and hydrodissection) and found that it was superior to the submerged cornea using backgrounds away (SCUBA) peeling technique with regard to cell loss (Stoeger www.corneajrnl.com |
557
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Cornea Volume 34, Number 5, May 2015
Brissette et al
CG. A laboratory comparison of endothelial cell loss using two techniques for DMEK tissue preparation, ARVO 2013). To date, no study has independently evaluated the time to donor graft preparation, the number of tears, or the pattern of cell staining using this novel technique. The purpose of this study was to compare a new method for harvesting endothelial donor grafts for DMEK, known as the Muraine technique, to the current SCUBA peeling technique in donor research eyes. We aimed to elucidate if the Muraine technique of DM harvesting is associated with a faster time of donor graft preparation and fewer graft tears. We also qualitatively evaluated the pattern of endothelial staining, as limiting endothelial cell loss is paramount to ensuring long-term graft survival in patients with endothelial dysfunction.
MATERIALS AND METHODS This study was a prospective ex vivo investigation. The University of Ottawa Research Ethics Board granted ethics approval. Twenty donor corneas were prepared for DMEK using the Muraine technique, and 20 donor corneas using the SCUBA technique at the Eye Institute’s Ophthalmic Simulation Surgery Centre. A corneal surgeon (K.B.) and a corneal clinical fellow (S.Y.) prepared 10 donor corneas for each technique. Primary outcome measures were time to prepare the graft and number of graft tears. Secondary outcome measures evaluated the qualitative pattern of endothelial cell staining. Vision Blue solution (DORC, Zuidland, the Netherlands) was used to evaluate the overall pattern of endothelial cell staining resulting from each technique. Digital pictures were taken through the operating microscope before and after donor graft preparation, and the patterns of staining were evaluated. Three independent investigators evaluated the pattern of staining of the grafts prepared by the corneal surgeon; patterns were defined as central, peripheral, or diffuse, and rated as mild, moderate, or severe.
DM outside the punch area. A delamination plane was initiated under the hinged graft area with the use of curved forceps. DM was hydrodissected with a 27-gauge cannula on a 5 mL syringe of BSS. Once the apex was reached, hydrodissection was extended to the left and right of the trephination edges to completely detach DM.
SCUBA Technique8 The donor corneoscleral rim was placed on a Barron donor corneal punch (Barron Precision Instruments LLC, Grand Blanc, MI). A 10-mm manual trephine was used to create a 10-mm circular cleavage border through DM. The donor corneoscleral rim was then stained with Vision Blue to highlight the scoring mark and after adequate staining, the cornea was submersed in BSS. A MicroFinger (Moria) was used to dissociate and peel for 360 degrees the periphery of the 10-mm-diameter tissue from the stroma. Once the periphery of this 10-mm-diameter tissue was peeled centrally approximately 0.5 to 1.0 mm from the edge, DM was grasped with fine nontoothed forceps and slowly stripped completely away from the stroma toward the center, taking care to leave the center attached. The donor tissue was then laid back in place and the central 8 mm was punched using an 8-mm Barron donor punch, freed of any tags or adhesions, grasped at the 8 mm edge, and the scroll was then detached completely from the stroma.
RESULTS
The donor corneoscleral rim was centered on the Muraine Punch block with the endothelium facing up. Balanced salt solution (BSS) was placed on the center of the graft. Suction was applied and the donor cornea was punched. The Muraine punch has a 8 mm diameter, a preset depth of 200 mm, and 2 opposite 3-mm segments of the circumference that do not cut and leave intact, hinged areas of DM. The donor cornea was removed from the punch, flipped “inside out,” placed endothelial side up on the artificial anterior chamber, and the cover was placed over the cornea to seal the chamber. The chamber was inflated with an air syringe and the valve was closed to stabilize the chamber. A lower pressure was maintained in the artificial anterior chamber than would be used in DSAEK graft preparation to allow for easier dissection of the donor tissue from the stroma. Vision Blue was used to stain the area of the punch while cohesive viscoelastic was applied to the center of the graft for protection. Forceps were used to peel the peripheral
The Fisher exact test and 2-sample Mann–Whitney U test were performed for statistical analysis of dichotomous and nonparametric continuous variables, respectively. When comparing the time between the surgeon and fellow, median time for donor DM graft preparation using the SCUBA technique was 301 6 85 seconds for the surgeon and 523 6 58 seconds for the clinical fellow (statistical significant difference, P = 0.0005). Donor DM graft preparation time using the Muraine technique was 359 6 84 seconds for the surgeon and 543 6 44 seconds for the clinical fellow (statistical significant difference, P = 0.002). When comparing the time between techniques for each person, although the SCUBA technique demonstrated a faster time, the results were not statistically significant for the surgeon or fellow (surgeon, P = 0.33; fellow, P = 0.24; pooled P = 0.46). Five peripheral graft tears (1 radial tear and 1 punchthrough hole for surgeon; 3 radial tears for fellow) occurred using the Muraine technique during uphill graft hydrodissection. These tears did not preclude potential usage as donor tissue. In comparison, there were no graft tears using the SCUBA technique. The difference in graft tears between the 2 techniques was statistically significant (P = 0.047). The endothelial cell staining pattern poststripping was qualitatively evaluated using Vision Blue in surgeon-prepared donor DM grafts only. In the grafts prepared using the Muraine technique, moderate central changes were observed in 2 grafts (Fig. 1), no staining was observed in 6 grafts, and no extra staining was seen beyond the tears in the 2 grafts that had tears. With regard to the SCUBA technique, 2 grafts showed moderate peripheral changes (Fig. 1), and no staining was seen in the remaining 8 grafts.
558
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Donor Graft Preparation Muraine Technique15
| www.corneajrnl.com
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Cornea Volume 34, Number 5, May 2015
FIGURE 1. Donor tissue before (A) and after (B) stripping using Muraine technique (showing more central staining). Donor tissue before (C) and after (D) stripping using SCUBA technique (showing more peripheral staining).
DISCUSSION This study represents an initial evaluation of a new surgical technique for DMEK donor graft preparation. The study evaluated important parameters that must all be considered when a surgeon is deciding to adopt a new technique over the current surgical standard. Time to prepare donor grafts was similar between the 2 techniques for both the corneal surgeon and corneal fellow. Donor preparation by the fellow was statistically significantly longer than donor preparation by the surgeon. Also, the Muraine technique showed central staining in 2 grafts, whereas the SCUBA technique showed peripheral staining in 2 grafts. This pattern of staining may represent the areas of the donor tissue that are most manipulated during tissue preparation (centrally for the Muraine technique and peripherally for the SCUBA technique). Although there was a statistically significant difference in the number of donor graft tears in the Muraine group, this could be attributed to the learning curve of adopting a new graft harvesting technique for both the corneal surgeon and corneal clinical fellow. To limit bias toward a more familiar SCUBA technique, both the surgeon and fellow had 10 practice procedures with the Muraine technique before starting the study. Both techniques were new for the fellow; however, the staff had previously performed numerous surgeries using the SCUBA technique and a few using the Muraine technique. As tears in the Muraine technique occurred during uphill dissection in an appropriately pressurized artificial anterior chamber, refinement of the technique may be to use a blunter duckbilled cannula rather than a “sharper” round cannula. The main limitation of our study is that the evaluation of the total pattern of endothelial staining is not on a validated scale. Another study has looked at ECD postgraft harvesting; however, our goal was to evaluate the total corneal pattern rather than evaluating a small subset of endothelium that may miss many peripheral changes.15 In addition, we did not want to incorporate any staining changes that resulted from the tissue manipulation required to get an endothelial cell count Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Muraine Versus SCUBA Peeling Technique
from donor DMEK tissue. To minimize bias in corneal evaluation, we employed 3 separate investigators to grade endothelial layer staining changes observed in the donor grafts from prestripping to poststripping. An area of future study would be to evaluate the clinical implications of the different staining patterns between the 2 techniques. In this ex vivo study, we found comparable time results between the Muraine technique and the SCUBA technique. However, there was a statistically significant difference in the rate of graft tears in the Muraine technique. Given the incidence of graft tears in the Muraine group and the need for specialized equipment (the Muraine punch), we conclude that the SCUBA technique may be superior for the preparation of endothelial donor grafts for DMEK. However, with further refinement, this new technique has the potential to be a reliable alternative method. A future direction would be to further evaluate this new technique in a larger clinical study to examine its potential usage in surgical practice. REFERENCES 1. Price FW Jr, Price MO. Descemet’s stripping with endothelial keratoplasty in 50 eyes: a refractive neutral corneal transplant. J Refractive Surg. 2005;21:339–345. 2. Price FW Jr, Price MO. Descemet’s stripping with endothelial keratoplasty in 200 eyes: early challenges and techniques to enhance donor adherence. J Cataract Refract Surg. 2006;32:411–418. 3. Terry MA, Ousley PJ. Deep lamellar endothelial keratoplasty in the first united states patients: early clinical results. Cornea. 2001;20: 239–243. 4. Terry MA, Ousley PJ. Small-incision deep lamellar endothelial keratoplasty (DLEK): six-month results in the first prospective clinical study. Cornea. 2005;24:59–65. 5. Melles GR, Ong TS, Ververs B, et al. Descemet membrane endothelial keratoplasty (DMEK). Cornea. 2006;25:987–990. 6. 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.e2. 7. 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. 8. 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. 9. Bahar I, Kaiserman I, McAllum P, et al. Comparison of posterior lamellar keratoplasty techniques to penetrating keratoplasty. Ophthalmology. 2008;115:1525–1533. 10. Anshu A, Price MO, Price FW Jr. Risk of corneal transplant rejection significantly reduced with descemet’s membrane endothelial keratoplasty. Ophthalmology. 2012;119:536–540. 11. Krabcova I, Studeny P, Jirsova K. Endothelial cell density before and after the preparation of corneal lamellae for descemet membrane endothelial keratoplasty with a stromal rim. Cornea. 2011;30:1436– 1441. 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. Busin M, Scorcia V, Patel AK, et al. Pneumatic dissection and storage of donor endothelial tissue for descemet’s membrane endothelial keratoplasty: a novel technique. Ophthalmology. 2010;117:1517–1520. 14. Studeny P, Farkas A, Vokrojova M, et al. Descemet membrane endothelial keratoplasty with a stromal rim (DMEK-S). Br J Ophthalmol. 2010;94:909–914. 15. Muraine M, Gueudry J, He Z, et al. Novel technique for the preparation of corneal grafts for descemet membrane endothelial keratoplasty. Am J Ophthalmol. 2013;156:851–859.
www.corneajrnl.com |
559
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Evaluation of a New Technique for Preparation of Endothelial Grafts for Descemet Membrane Endothelial Keratoplasty Ashley Brissette, MD,* Ronan Conlon, MD,† Joshua C Teichman, MD, MPH, FRCSC,† Season Yeung, MBBS, FRANZCO,† Setareh Ziai, MD, FRCSC,† and Kashif Baig, MD, MBA, FRCSC†
Purpose: The purpose of this study was to compare the Muraine technique, a relatively new method for preparing endothelial grafts for Descemet membrane endothelial keratoplasty (DMEK), with the current standard submerged cornea using backgrounds away (SCUBA) peeling technique.
Methods: This study was a prospective ex vivo investigation. In a wet-lab setting, 20 donor corneas were prepared for DMEK using The Muraine technique and 20 donor corneas using the SCUBA technique. In each of the technique groups, 10 corneas were prepared by a corneal surgeon and 10 were prepared by a corneal fellow. Primary outcome measures were the time needed to prepare endothelial grafts and the number of graft tears.
Results: In the SCUBA technique, median time to prepare grafts was shorter for both the surgeon (301 6 85 seconds) and fellow (523 6 58 seconds) compared with the Muraine technique (surgeon, 359 6 83 seconds; fellow, 543 6 44 seconds). However, these findings were not statistically significant (surgeon, P = 0.33; fellow, P = 0.24; pooled, P = 0.46). There was a statistically significant difference between surgeon time and fellow time for each technique (SCUBA technique, P = 0.0005; Muraine technique, P = 0.002). In the Muraine technique, there were 5 graft tears (surgeon = 2, fellow = 3), and no graft tears in the SCUBA technique, which was statistically significant (P = 0.047). Conclusions: The present study demonstrates that the SCUBA technique may be a more effective technique to prepare endothelial donor grafts for DMEK. Key Words: Descemet membrane endothelial keratoplasty, Muraine technique, submerged cornea using backgrounds away, transplant technique, donor graft (Cornea 2015;34:557–559)
Received for publication September 12, 2014; revision received January 2, 2015; accepted January 11, 2015. Published online ahead of print March 6, 2015. From the *Department of Ophthalmology, Queen’s University, Kingston, ON, Canada; and †University of Ottawa Eye Institute, Ottawa, ON, Canada. The authors have no funding or conflicts of interest to disclose. Reprints: Kashif Baig, MD, MBA, FRCSC, University of Ottawa Eye Institute, 501 Smyth Rd, Suite W6223, Ottawa, ON K1H 8L6, Canada (e-mail: [email protected]). Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Cornea Volume 34, Number 5, May 2015
T
he best possible visual outcome in posterior corneal disease requiring transplantation relies on selective transplantation of only Descemet membrane (DM) and endothelium, producing an anatomically pure replacement of what is removed. One of the first described techniques for preparing posterior corneal grafts was deep lamellar endothelial keratoplasty (DLEK), which was then refined to Descemet stripping (automated) endothelial keratoplasty (DSEK/ DSAEK).1–4 Further selective transplantation of only DM and endothelial layers led to the development of Descemet membrane endothelial keratoplasty (DMEK).5 DMEK has the advantage of being minimally invasive and offers more rapid visual recovery than penetrating keratoplasty.6–8 Studies have shown less graft rejection with DMEK, and it also has the advantage of leading to more predictable refractive outcomes after transplantation by eliminating donor stromal thickness and contour.7,9,10 A critical step in DMEK surgery is preparing donor DM to minimize trauma because the delicate DM is prone to tears and endothelial cell loss.11 Proper donor tissue harvesting techniques are essential to maximize preservation of donor endothelial cell density (ECD) to secure long-term graft survival and reduce the loss of precious donor tissue.12 An effective and reproducible donor graft harvesting technique is required, and modifications of techniques are frequently published.7,11,13,14 A recent report outlined a new method for preparing endothelial grafts for DMEK, the Muraine technique.15 The Muraine Punch (Moria, Antony, France) and an artificial anterior chamber are used for this procedure. The authors of the report demonstrated that both histologic and electron microscopic sections confirmed the cleavage between DM and posterior stroma on the corneas used for research. Also, there was minimal change to ECDs before and after dissection using the Muraine technique. Clinically, the authors reported ECDs of 2656 6 28 cells per square millimeter (range, 2450–3100 cells/mm2) preoperatively and 1658 6 43 cells per square millimeter (range, 900–2600 cells/ mm2) 6 months postoperatively.15 Thus, the authors concluded that the Muraine technique was a reliable technique for preparing DM grafts. Recently, a study by Stoeger et al evaluated the ECDs after the Muraine technique (using partial trephination and hydrodissection) and found that it was superior to the submerged cornea using backgrounds away (SCUBA) peeling technique with regard to cell loss (Stoeger www.corneajrnl.com |
557
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Cornea Volume 34, Number 5, May 2015
Brissette et al
CG. A laboratory comparison of endothelial cell loss using two techniques for DMEK tissue preparation, ARVO 2013). To date, no study has independently evaluated the time to donor graft preparation, the number of tears, or the pattern of cell staining using this novel technique. The purpose of this study was to compare a new method for harvesting endothelial donor grafts for DMEK, known as the Muraine technique, to the current SCUBA peeling technique in donor research eyes. We aimed to elucidate if the Muraine technique of DM harvesting is associated with a faster time of donor graft preparation and fewer graft tears. We also qualitatively evaluated the pattern of endothelial staining, as limiting endothelial cell loss is paramount to ensuring long-term graft survival in patients with endothelial dysfunction.
MATERIALS AND METHODS This study was a prospective ex vivo investigation. The University of Ottawa Research Ethics Board granted ethics approval. Twenty donor corneas were prepared for DMEK using the Muraine technique, and 20 donor corneas using the SCUBA technique at the Eye Institute’s Ophthalmic Simulation Surgery Centre. A corneal surgeon (K.B.) and a corneal clinical fellow (S.Y.) prepared 10 donor corneas for each technique. Primary outcome measures were time to prepare the graft and number of graft tears. Secondary outcome measures evaluated the qualitative pattern of endothelial cell staining. Vision Blue solution (DORC, Zuidland, the Netherlands) was used to evaluate the overall pattern of endothelial cell staining resulting from each technique. Digital pictures were taken through the operating microscope before and after donor graft preparation, and the patterns of staining were evaluated. Three independent investigators evaluated the pattern of staining of the grafts prepared by the corneal surgeon; patterns were defined as central, peripheral, or diffuse, and rated as mild, moderate, or severe.
DM outside the punch area. A delamination plane was initiated under the hinged graft area with the use of curved forceps. DM was hydrodissected with a 27-gauge cannula on a 5 mL syringe of BSS. Once the apex was reached, hydrodissection was extended to the left and right of the trephination edges to completely detach DM.
SCUBA Technique8 The donor corneoscleral rim was placed on a Barron donor corneal punch (Barron Precision Instruments LLC, Grand Blanc, MI). A 10-mm manual trephine was used to create a 10-mm circular cleavage border through DM. The donor corneoscleral rim was then stained with Vision Blue to highlight the scoring mark and after adequate staining, the cornea was submersed in BSS. A MicroFinger (Moria) was used to dissociate and peel for 360 degrees the periphery of the 10-mm-diameter tissue from the stroma. Once the periphery of this 10-mm-diameter tissue was peeled centrally approximately 0.5 to 1.0 mm from the edge, DM was grasped with fine nontoothed forceps and slowly stripped completely away from the stroma toward the center, taking care to leave the center attached. The donor tissue was then laid back in place and the central 8 mm was punched using an 8-mm Barron donor punch, freed of any tags or adhesions, grasped at the 8 mm edge, and the scroll was then detached completely from the stroma.
RESULTS
The donor corneoscleral rim was centered on the Muraine Punch block with the endothelium facing up. Balanced salt solution (BSS) was placed on the center of the graft. Suction was applied and the donor cornea was punched. The Muraine punch has a 8 mm diameter, a preset depth of 200 mm, and 2 opposite 3-mm segments of the circumference that do not cut and leave intact, hinged areas of DM. The donor cornea was removed from the punch, flipped “inside out,” placed endothelial side up on the artificial anterior chamber, and the cover was placed over the cornea to seal the chamber. The chamber was inflated with an air syringe and the valve was closed to stabilize the chamber. A lower pressure was maintained in the artificial anterior chamber than would be used in DSAEK graft preparation to allow for easier dissection of the donor tissue from the stroma. Vision Blue was used to stain the area of the punch while cohesive viscoelastic was applied to the center of the graft for protection. Forceps were used to peel the peripheral
The Fisher exact test and 2-sample Mann–Whitney U test were performed for statistical analysis of dichotomous and nonparametric continuous variables, respectively. When comparing the time between the surgeon and fellow, median time for donor DM graft preparation using the SCUBA technique was 301 6 85 seconds for the surgeon and 523 6 58 seconds for the clinical fellow (statistical significant difference, P = 0.0005). Donor DM graft preparation time using the Muraine technique was 359 6 84 seconds for the surgeon and 543 6 44 seconds for the clinical fellow (statistical significant difference, P = 0.002). When comparing the time between techniques for each person, although the SCUBA technique demonstrated a faster time, the results were not statistically significant for the surgeon or fellow (surgeon, P = 0.33; fellow, P = 0.24; pooled P = 0.46). Five peripheral graft tears (1 radial tear and 1 punchthrough hole for surgeon; 3 radial tears for fellow) occurred using the Muraine technique during uphill graft hydrodissection. These tears did not preclude potential usage as donor tissue. In comparison, there were no graft tears using the SCUBA technique. The difference in graft tears between the 2 techniques was statistically significant (P = 0.047). The endothelial cell staining pattern poststripping was qualitatively evaluated using Vision Blue in surgeon-prepared donor DM grafts only. In the grafts prepared using the Muraine technique, moderate central changes were observed in 2 grafts (Fig. 1), no staining was observed in 6 grafts, and no extra staining was seen beyond the tears in the 2 grafts that had tears. With regard to the SCUBA technique, 2 grafts showed moderate peripheral changes (Fig. 1), and no staining was seen in the remaining 8 grafts.
558
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Donor Graft Preparation Muraine Technique15
| www.corneajrnl.com
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Cornea Volume 34, Number 5, May 2015
FIGURE 1. Donor tissue before (A) and after (B) stripping using Muraine technique (showing more central staining). Donor tissue before (C) and after (D) stripping using SCUBA technique (showing more peripheral staining).
DISCUSSION This study represents an initial evaluation of a new surgical technique for DMEK donor graft preparation. The study evaluated important parameters that must all be considered when a surgeon is deciding to adopt a new technique over the current surgical standard. Time to prepare donor grafts was similar between the 2 techniques for both the corneal surgeon and corneal fellow. Donor preparation by the fellow was statistically significantly longer than donor preparation by the surgeon. Also, the Muraine technique showed central staining in 2 grafts, whereas the SCUBA technique showed peripheral staining in 2 grafts. This pattern of staining may represent the areas of the donor tissue that are most manipulated during tissue preparation (centrally for the Muraine technique and peripherally for the SCUBA technique). Although there was a statistically significant difference in the number of donor graft tears in the Muraine group, this could be attributed to the learning curve of adopting a new graft harvesting technique for both the corneal surgeon and corneal clinical fellow. To limit bias toward a more familiar SCUBA technique, both the surgeon and fellow had 10 practice procedures with the Muraine technique before starting the study. Both techniques were new for the fellow; however, the staff had previously performed numerous surgeries using the SCUBA technique and a few using the Muraine technique. As tears in the Muraine technique occurred during uphill dissection in an appropriately pressurized artificial anterior chamber, refinement of the technique may be to use a blunter duckbilled cannula rather than a “sharper” round cannula. The main limitation of our study is that the evaluation of the total pattern of endothelial staining is not on a validated scale. Another study has looked at ECD postgraft harvesting; however, our goal was to evaluate the total corneal pattern rather than evaluating a small subset of endothelium that may miss many peripheral changes.15 In addition, we did not want to incorporate any staining changes that resulted from the tissue manipulation required to get an endothelial cell count Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Muraine Versus SCUBA Peeling Technique
from donor DMEK tissue. To minimize bias in corneal evaluation, we employed 3 separate investigators to grade endothelial layer staining changes observed in the donor grafts from prestripping to poststripping. An area of future study would be to evaluate the clinical implications of the different staining patterns between the 2 techniques. In this ex vivo study, we found comparable time results between the Muraine technique and the SCUBA technique. However, there was a statistically significant difference in the rate of graft tears in the Muraine technique. Given the incidence of graft tears in the Muraine group and the need for specialized equipment (the Muraine punch), we conclude that the SCUBA technique may be superior for the preparation of endothelial donor grafts for DMEK. However, with further refinement, this new technique has the potential to be a reliable alternative method. A future direction would be to further evaluate this new technique in a larger clinical study to examine its potential usage in surgical practice. REFERENCES 1. Price FW Jr, Price MO. Descemet’s stripping with endothelial keratoplasty in 50 eyes: a refractive neutral corneal transplant. J Refractive Surg. 2005;21:339–345. 2. Price FW Jr, Price MO. Descemet’s stripping with endothelial keratoplasty in 200 eyes: early challenges and techniques to enhance donor adherence. J Cataract Refract Surg. 2006;32:411–418. 3. Terry MA, Ousley PJ. Deep lamellar endothelial keratoplasty in the first united states patients: early clinical results. Cornea. 2001;20: 239–243. 4. Terry MA, Ousley PJ. Small-incision deep lamellar endothelial keratoplasty (DLEK): six-month results in the first prospective clinical study. Cornea. 2005;24:59–65. 5. Melles GR, Ong TS, Ververs B, et al. Descemet membrane endothelial keratoplasty (DMEK). Cornea. 2006;25:987–990. 6. 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.e2. 7. 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. 8. 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. 9. Bahar I, Kaiserman I, McAllum P, et al. Comparison of posterior lamellar keratoplasty techniques to penetrating keratoplasty. Ophthalmology. 2008;115:1525–1533. 10. Anshu A, Price MO, Price FW Jr. Risk of corneal transplant rejection significantly reduced with descemet’s membrane endothelial keratoplasty. Ophthalmology. 2012;119:536–540. 11. Krabcova I, Studeny P, Jirsova K. Endothelial cell density before and after the preparation of corneal lamellae for descemet membrane endothelial keratoplasty with a stromal rim. Cornea. 2011;30:1436– 1441. 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. Busin M, Scorcia V, Patel AK, et al. Pneumatic dissection and storage of donor endothelial tissue for descemet’s membrane endothelial keratoplasty: a novel technique. Ophthalmology. 2010;117:1517–1520. 14. Studeny P, Farkas A, Vokrojova M, et al. Descemet membrane endothelial keratoplasty with a stromal rim (DMEK-S). Br J Ophthalmol. 2010;94:909–914. 15. Muraine M, Gueudry J, He Z, et al. Novel technique for the preparation of corneal grafts for descemet membrane endothelial keratoplasty. Am J Ophthalmol. 2013;156:851–859.
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559
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