Corneal Guttae After Descemet Membrane Endothelial Keratoplasty.

PURPOSE: The aim of this study was to report on the occurrence of corneal guttae after Descemet membrane endothelial keratoplasty (DMEK). METHODS: In this retrospective case series, 13 eyes of 13 patients who underwent DMEK at 2 tertiary referral centers between 2007 and 2021 (average available follow-up 73 ± 52 months, range 18-174 months) and showed corneal guttae during postoperative examinations were included. Eye bank images were retrospectively reviewed. RESULTS: Occurrence of guttae was observed by specular microscopy in 13 eyes. In 11 cases, presence of guttae was confirmed by confocal microscopy and in 1 case by histology. Five eyes showed an increase in guttae density during the postoperative course. Surgery indications were Fuchs endothelial corneal dystrophy (n = 11), pseudophakic bullous keratopathy (n = 1), and DMEK graft failure after allograft rejection (n = 1); the latter eye had shown no signs of guttae after primary DMEK. Two eyes with guttae required a repeat DMEK due to graft failure. At the last available follow-up, all 11 remaining eyes had clear corneas and 10 eyes had a best-corrected visual acuity of ≥0.9 (decimal). During donor cornea processing in the eye bank, no guttae were observed on the donor tissue. CONCLUSIONS: Corneal guttae can occur after DMEK including in eyes operated for indications other than Fuchs endothelial corneal dystrophy and most likely guttae were present on the donor graft but were not detectable by routine slit-lamp and light microscopy evaluation in the eye bank. Postoperative guttae density varies among patients and especially small isolated guttae do not seem to affect clinical outcomes.

P07-A139†Guttae in corneal donor tissue.

PURPOSE: To report on the occurrence of guttae in corneal donor tissue. MATERIAL & METHODS: Retrospective database study of discard reasons for corneal donor tissue at Amnitrans EyeBank Rotterdam (AER) for the period from January 2019 to December 2021 and the outcome of an eight-question survey sent to European Eye Bank Association corresponding members addressing the occurrence of corneal guttae and the practice pattern regarding donor tissue with guttae. RESULTS: Between 2019 and 2021 6039 donor corneas were processed at AER. Average discard rate because of guttae in this period was 9 (±4)% (n=552). Most corneas were discarded because of guttae at first evaluation (8%, n=481). Monthly discard rate because of guttae ranged from 3% to 19%. Yearly discard rates related to corneal guttae were 10 (±3)%, 8 (±3)% and 11 (±5)% in 2019, 2020 and 2021, respectively. Average endothelial cell density (ECD) at the first evaluation from 2019-2021 was 2486 (±93) cells/mm2, with average monthly ECD ranging from 2343 to 2642 cells/mm2.Twenty-nine eye banks completed the survey, including 4 located outside Europe. 70% reported a guttae-related discard rate of ≤4. The types of microscope used for the evaluation, the geographical location and the number of guttae permitted do not seem to influence the discard rates. 13 eye banks permitted 0 guttae while 10 banks accepted between 1-10 guttae.The 16 eye banks that responded 'no' to the question whether the contralateral cornea of a guttae-cornea was automatically discarded did report a lower guttae-related discard rate than the other eye banks. CONCLUSION: The high variability of the discard rate due to guttae in donor corneas (ranging from <1% and >12%) is an indication that it is not always easy to detect guttae in donor corneas. Although transplanting corneal grafts with guttae does not necessarily mean that a re-transplantation will be needed on the short term, a vital method to unequivocally determine the presence of guttae in the eye bank seems essential to prevent unnecessary waste of suspect tissue and unnecessary re-surgeries.

32†Corneal guttae after descemet membrane endothelial keratoplasty (DMEK).

PURPOSE: To report on the occurrence of corneal guttae after Descemet membrane endothelial keratoplasty (DMEK) in eyes operated on for Fuchs endothelial corneal dystrophy (FECD). MATERIAL AND METHODS: Case series of 10 eyes of 10 patients operated on for FECD at a tertiary referral center between 2008 and 2019. Average patient age was 61±12 years and 3 patients were female and 6 were male. Five patients were phakic and 4 pseudophakic. Average donor age was 67±9 years. RESULTS: During routine postoperative consultation, specular microscopy images showed suspected recurrence of guttae in 10 eyes after DMEK. Presence of guttae was subsequently confirmed in 9 cases by confocal microscopy and in one case by histology. Six out of 10 patients (60%) had undergone bilateral DMEK, but all only showed recurrence of guttae in one eye. In 9 eyes guttae recurred after primary DMEK, while in one eye recurrence was after a re-DMEK that has been performed 56 months after the first DMEK with no signs of guttae after primary DMEK. Suspected guttae were visible on specular microscopy images already at 1 month after DMEK in most cases.No guttae had been noted during donor cornea processing in the eye bank. Preoperative donor endothelial cell density (ECD) had been 2643±145 cells/mm2 and 1-year postoperative ECD was 1047±458 cells/mm2 (n=8). CONCLUSION: Recurrence of guttae after DMEK is most likely due to guttae on the donor graft that were not detectable by routine slit-lamp and light-microscopy evaluation in the eye bank. Better screening methods for guttae detection need to be developed for eye banks to avoid releasing tissue for transplantation that contains guttae or is prone for postoperative guttae formation.

24†Effect of graft preparation techniques on clinical outcomes after Descemet membrane endothelial keratoplasty (DMEK).

PURPOSE: To compare the clinical outcomes after Descemet membrane endothelial keratoplasty (DMEK) for grafts prepared by the manual no-touch peeling technique and grafts prepared by a modified liquid bubble technique. MATERIAL AND METHODS: For this study, 236 DMEK grafts were included that were prepared at Amnitrans EyeBank Rotterdam by experienced eye bank personnel. 132 grafts were prepared by using the 'no-touch' DMEK preparation technique and 104 grafts by using a modified liquid bubble technique. The liquid bubble technique was modified to render it a no-touch technique while maintaining the ability to save the anterior donor button as a potential Deep Anterior lamellar keratoplasty (DALK) or Bowman layer (BL) graft. DMEK surgeries were performed at Melles Cornea Clinic Rotterdam by experienced DMEK surgeons. All patients underwent DMEK for Fuchs endothelial dystrophy. Average patient age was 68 (±10) years and average donor age was 69 (±9) years with no difference between the two groups. Endothelial cell density (ECD) was evaluated after graft preparation by light microscopy in the eye bank and at 6-month postoperatively by specular microscopy. RESULTS: Endothelial cell density (ECD) decreased from 2705 (±146) cells/mm2 (n=132) before to 1570 (±490) cells/mm2 (n=130) at 6 months postoperatively for grafts prepared by the no-touch technique. For grafts prepared by the modifiedliquid bubble technique, ECD decreased from 2627 (±181) cells/mm2 (n=104) before to 1553 (±513) cells/mm2 (n=103) after surgery. Postoperative ECD did not differ for grafts prepared by the two techniques (P=0.79). Central corneal thickness (CCT) decreased from 660 (±124) µm to 513 (±36) µm postoperatively in the no-touch group and from 684 (±116) µm to 515 (±35) µm postoperatively in the modified liquid bubble group, with no postoperative CCT difference between groups (P=0.59). In total 3 eyes underwent re-surgery within the study period (n=2 (1.5%) in the no-touch group, n=1 (1.0%) in the liquid bubble group; P=0.71) and 26 eyes required a re-bubbling procedure for incomplete graft adherence (n=16 (12%) in the no-touch group, n=10 (10%) in the liquid bubble group; P=0.37). CONCLUSION: Clinical outcomes after DMEK are comparable for grafts prepared by either the manual no-touch peeling technique or the modified liquid bubble technique. While both techniques are safe and useful techniques to prepare DMEK grafts, the modified liquid bubble technique offers advantages for corneas with scars.

Preclinical testing of small diameter Descemet membrane endothelial keratoplasty grafts to increase tissue availability.

In this study, we describe a process of preparing, surgically manipulating, and validating a novel "small diameter" 4mm circular Descemet membrane endothelial keratoplasty (DMEK) graft in vitro. Three small diameter DMEK grafts can be prepared from a single donor endothelium and could, therefore, potentially expand the donor pool. Prior to clinical use, however, we aimed to examine each step of the process to determine the effect on the endothelial cell loss and whether or not cells retained their capacity to migrate uniformly. For this study, circular small diameter grafts, obtained from twelve corneas of ten donors deemed ineligible for transplantation, were included. Small diameter DMEK graft preparation was successful in all cases (n = 36). Endothelial cell density (ECD), determined in the eye bank on seventeen grafts, showed an average decrease from 2413 (±189) cells/mm2 before to 2240 (±413) cells/mm2 after preparation. Twenty-four grafts were used to simulate DMEK-surgery in vitro and were successfully stained with 0.06% trypan blue, loaded into a straight DMEK-injector, unfolded, positioned, and centered within the circular ~ 4mm descemetorhexis. The estimated % area populated by viable cells on the grafts decreased from on average 92 (±3) % before to 78 (±10) % (n = 4) after in vitro surgery. Cells displayed a capacity for uniform cell migration from all edges of the graft (n = 4) when embedded in the 3D hydrogel system. Our data show, that by using an in vitro model of DMEK-surgery it was possible to test the 4mm circular DMEK grafts from eye bank preparation to surgical implantation. The cell loss after in vitro surgery was comparable with the in vivo ECD decline early after DMEK and the capacity of the cells to migrate to potentially cover bare stroma indicates that these small diameter grafts may be a viable clinical option to treat central endothelial disease.

In Vitro Evaluation and Transplantation of Human Corneal Endothelial Cells Cultured on Biocompatible Carriers.

Corneal transplantation is currently the only effective treatment option for dysfunctional corneal endothelial cells (CEC). In this study, we test in vitro the surgical potential of cultivated human corneal endothelial cells (hCEC) on human anterior lens capsule (HALC), LinkCell™ bioengineered collagen sheets of 20-µm thickness (LK20), and denuded Descemet membrane (dDM) as tissue-engineered grafts for Descemet membrane (DM) endothelial keratoplasty (DMEK) to bypass the problem of donor tissue availability. Primary hCEC cultured on all carriers formed a monolayer of tightly packed cells with a high cell viability rate (96% ± 4%). hCEC on HALC and LK20 showed unremarkable expression of zonula occludens-1 (ZO-1) and Na+/K+-adenosine triphosphatase (ATPase), while Na+/K+-ATPase expression of cells seeded on dDM was mainly cytoplasmic. All hCEC-carrier constructs were evaluated by simulating DMEK surgery in vitro using a human donor cornea without DM mounted on an artificial anterior chamber (AC) and a regular DMEK-graft used as a surgical reference model. During in vitro surgery, hCEC-HALC constructs behaved most similarly to a DMEK-graft during implantation and unfolding, showing good adhesion to the bare stroma. On the other hand, hCEC-LK20 and hCEC-dDM constructs required some additional handling because of challenges related to the surgical procedure, although they were both successfully unfolded and implanted in the artificial AC. The hCEC-dDM constructs showed similar graft adherence as hCEC-HALC constructs, while adherence of hCEC-LK20 constructs was less effective. After the in vitro surgery, the estimated area populated by viable cells on the hCEC-HALC and hCEC-LK20 constructs was ∼83% and ∼67%, respectively. Overall, hCEC-HALC constructs behaved most similarly to a DMEK-graft during in vitro DMEK surgery, while graft adhesion and surgical handling, respectively, are parameters still requiring optimization for hCEC-LK20 and hCEC-dDM constructs.

In vitro endothelial cell migration from limbal edge-modified Quarter-DMEK grafts.

Endothelial cell migration plays a crucial role in achieving corneal clearance after corneal transplantation when using smaller-sized endothelial grafts to increase the donor pool. In this study we investigated how different strategies of Quarter-Descemet Membrane Endothelial Keratoplasty (Quarter-DMEK) limbal graft edge modification influence peripheral endothelial cell migration in an in vitro culture environment. For this study, 15 Quarter-DMEK grafts, prepared from 7 corneas deemed ineligible for transplantation but with intact and viable endothelial cells, were embedded in a cooled biocompatible, thermoresponsive matrix for culture. The limbal edge of ten Quarter-DMEK grafts were modified, either by using a small diameter punch or by peripheral radial cuts. All Quarter-DMEK grafts showed substantial collective endothelial cell migration from the radial cut graft edges, as observed by light microscopy at standardized time intervals. Grafts were retrieved from the polymer matrix after the two-week culture for immunohistochemistry analyses of the newly formed cell monolayers; this demonstrated the presence of tightly packed and viable cells that showed higher migratory ability at the leading edge. Peripheral endothelial cell migration, however, was not triggered by increasing cell exposure to free space through surgical modifications of the far periphery. Our data suggest that alterations in the far peripheral area of Quarter-DMEK grafts were insufficient to triggering cell migration from the limbal graft edge. This may be due to transient-amplifying cells that reside in the far periphery and which lack cytokinetic directional cues. Understanding the migration capacity of the peripheral endothelium could unlock cells' therapeutic potential which are, at present, routinely discarded from transplantation. Encouraging peripheral cell migration may also improve clinical outcomes from Quarter-DMEK, but a more effective solution is required prior to clinical implementation of modified grafts.

Asymmetrical endothelial cell migration from in vitro Quarter-Descemet membrane endothelial keratoplasty grafts.

PURPOSE: To investigate in vitro central and peripheral corneal endothelial cell (EC) migration from Quarter-Descemet membrane endothelial keratoplasty (Quarter-DMEK) grafts. METHODS: Quarter-DMEK grafts were obtained from 10 corneas ineligible for transplantation but with intact and viable ECs. Ten Quarter-DMEK grafts were 'sandwiched' between two glass slides and cultured over 1 week in a humidified atmosphere at 37 °C and 5% CO2 . Cell migration was evaluated by light microscopy at standardized time intervals. In addition, immunohistochemistry analyses were performed to assess the detailed structural organization of ECs in the corneal centre and far periphery. RESULTS: Endothelial cell (EC) migration occurred from the radial cut graft edges, but not from the far peripheral area. Cell migration followed three different migration patterns: (1) individual cell migration, (2) uncoordinated cell migration of cell clusters and (3) collective migration in which ECs moved as a sheet. Immunostaining showed the presence of ECs up to the far periphery but with different expression patterns of phenotypical markers ZO-1, Na+ /K+ -ATPase and vimentin compared to central ECs. CONCLUSION: In vitro EC migration from Quarter-DMEK grafts occurs along the radial cut edges with a decrease in migration activity towards the corneal far periphery. No migration occurred along the outer peripheral corneal edge possibly due to a different anatomical matrix in the far periphery. Hence, ECs from the far periphery may not contribute to corneal clearance of the adjacent bare area after Quarter-DMEK surgery, but these cells may constitute a valuable cellular reserve on the graft.

Quarter-Descemet membrane endothelial keratoplasty (Quarter-DMEK) for Fuchs endothelial corneal dystrophy: 6 months clinical outcome.

BACKGROUND/AIM: To assess the clinical outcome of the first series of Quarter-Descemet membrane endothelial keratoplasty (Quarter-DMEK), a potential hybrid technique between 'descemetorhexis only' and conventional, circular DMEK. METHODS: Prospective interventional case series at a tertiary referral centre. Twelve eyes of 12 patients with central Fuchs endothelial corneal dystrophy underwent Quarter-DMEK, that is, transplantation of one quadrant of a full-diameter DMEK graft, and were evaluated for best-corrected visual acuity (BCVA), endothelial cell density (ECD) and complications up to 6 months postoperatively. RESULTS: At 6 months postoperatively, all eyes reached a BCVA of ≥20/40 (≥0.5), 11/12 (92%) of ≥20/25 (≥0.8) and 6/12 (50%) of ≥20/20 (≥1.0). Mean central ECD decreased from 2867 (±161) cells/mm2 before to 1255 (±514) cells/mm2 at 1 month, 1058 (±455) cells/mm2 at 3 months and 968 (±427) cells/mm2 at 6 months after surgery. Rebubbling was performed in 4/12 eyes (33%) within the first two months. CONCLUSIONS: Quarter-DMEK may be a feasible procedure that allows for visual outcomes similar to conventional, circular DMEK. The relatively large drop in ECD within the first month may have resulted from more extensive endothelial cell migration and/or measurement error (at the graft edges). If longer-term outcomes would resemble those of conventional DMEK, Quarter-DMEK may potentially quadruple the availability of endothelial grafts.

Donor Tissue Preparation for Descemet Membrane Endothelial Keratoplasty: An Updated Review.

PURPOSE: To provide an overview of the current literature on donor tissue preparation for Descemet membrane endothelial keratoplasty (DMEK). METHODS: A comprehensive database search without date restrictions was performed in PubMed and in The Cochrane Library in May, 2017. Keywords included Descemet membrane endothelial keratoplasty, corneal transplantation, graft, harvest, dissection, preparation, endothelial cell, and endothelial cell density. Articles aiming to describe or evaluate a technique for DMEK graft preparation were considered eligible and were included in this review. RESULTS: A graft dissection technique that provides consistent tissue qualities and a low risk of preparation failure is essential for surgeons and eye banks preparing DMEK tissue. Various techniques have been described aiming to facilitate DMEK graft dissection, including manual dissection, pneumatic dissection, and hydrodissection. All show a trend toward a no-touch technique, for example, without direct physical tissue manipulation during tissue harvesting, as a potential ideal approach to minimize graft damage. CONCLUSIONS: An overview of the current harvesting techniques available for DMEK may benefit corneal surgeons and eye banks in choosing the best approach for each specific user.

Minimizing Graft Preparation Failure in Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To report the failure rate of 2 graft preparation techniques for Descemet membrane endothelial keratoplasty (DMEK) and to evaluate how to minimize graft preparation failure. METHODS: Retrospective, nonrandomized study at an eye bank specialized in graft preparation for lamellar keratoplasty. For 1416 donor corneas, the DMEK graft preparation failure rate was evaluated for 2 different techniques, technique I: "Standardized traditional technique" (n = 341) and technique II: "Standardized no-touch technique" (n = 933), and for grafts that were converted from technique II to technique I during preparation (n = 142). RESULTS: The overall failure rate averaged 3.9% (55/1416): 7.0% (24/341) for technique I and 2.9% (31/1075) for technique II (P < 0.05). Tissue preparations which were converted from technique II to technique I failed in 13.4% (19/142), whereas for grafts that were entirely prepared by technique II, the failure rate was only 1.3% (12/933). The endothelial cell density decrease (before compared with after preparation) did not differ for both techniques (1.1% vs. 0.2%, P > 0.05). CONCLUSIONS: Various DMEK graft preparation techniques may provide failure rates of <4%. A "no-touch preparation" approach (technique II) may combine good graft quality (completely intact endothelial cell layer, ie, negligible preparation-induced endothelial cell density decrease) with low risk of dissection failure, leaving the possibility of conversion to "traditional preparation" (technique I) as a backup method.

Case Report of Quarter-Descemet Membrane Endothelial Keratoplasty for Fuchs Endothelial Dystrophy.

PURPOSE: To describe a further modification of Descemet membrane endothelial keratoplasty (DMEK), using a quarter of an untrephined full-size donor Descemet membrane (DM) sheet ("Quarter-DMEK"). METHODS: A 58-year-old patient underwent Quarter-DMEK for Fuchs endothelial dystrophy in his pseudophakic right eye, with a single quadrant of a full-size, 11.5-mm-diameter DM graft. RESULTS: Best-corrected visual acuity improved from 20/50 (0.4) before surgery to 20/40 (0.5) at 1 day, 20/30 (0.7) at 1 week, 20/25 (0.8) at 1 month and 20/20 (1.0) at 3 months after surgery. Central endothelial cell density decreased from 2700 cells/mm before surgery to 1551 cells/mm at 1 week, 1104 cells/mm at 1 month, and 846 cells/mm at 3 months after surgery. Pachymetry returned to normal values within the first month. No complications were observed. CONCLUSIONS: Quarter-DMEK may give fast visual rehabilitation within the first month similar to visual outcomes after circular DMEK or semicircular DMEK (hemi-DMEK). If long-term endothelial cell density would prove acceptable in a larger number of cases, quarter-DMEK may have the potential to quadruple the availability of donor endothelial tissue for endothelial keratoplasty.

Donor Tissue Preparation for Bowman Layer Transplantation.

PURPOSE: To describe and compare 2 preparation techniques for Bowman layer (BL) grafts for use in BL transplantation. METHODS: A retrospective evaluation of the 2 methods for preparing BL grafts was performed, that is, BL graft preparation from donor globes not eligible for penetrating keratoplasty or endothelial keratoplasty (technique I, n = 36) and BL graft preparation from previously excised corneoscleral buttons (technique II, n = 36) that could not be used for PK or had been denuded of Descemet membrane and endothelium for Descemet membrane endothelial keratoplasty graft preparation. BL graft preparation difficulties were recorded, and the preparation failure rate was examined and compared between the techniques. RESULTS: Overall, BL graft preparation was successful in 51 cases (51/72; 70.8%), of which 25 preparations were successful using technique I, and 26 using technique II, representing a success rate of 69.4% (25/36) and 72.2% (26/36) for techniques I and II, respectively. Reasons for discarding a BL graft were tearing of the BL tissue during the preparation (n = 19) and stroma attached to the graft (n = 2). CONCLUSIONS: Isolated BL grafts can be prepared from both whole donor globes and corneoscleral rims with equivalent success. Preparation from corneoscleral rims may offer the advantage that, from one donor cornea, the posterior layers can be used for Descemet membrane endothelial keratoplasty graft preparation and the anterior part for BL graft preparation.

Graft preparation for hemi-Descemet membrane endothelial keratoplasty (hemi-DMEK).

BACKGROUND/AIMS: There is a substantial shortage of donor tissue for endothelial keratoplasty worldwide. Using two endothelial grafts of one donor cornea may potentially increase the pool of suitable donor tissue for Descemet membrane endothelial keratoplasty (DMEK). This study evaluates the technical feasibility of obtaining two DMEK grafts with a different (semicircular) shape, but similar surface area as a 'conventional' 8-9 mm circular transplant from a single donor cornea and to evaluate the viability of these grafts stored in organ-culture medium up to 5 weeks after graft preparation. METHODS: Ten human corneas not suitable for transplantation were used for preparation of semicircular-shaped grafts (hemi-DMEK grafts). The viability of these hemi-DMEK grafts was measured by evaluating the endothelial cell density (ECD) with light microscopy before and immediately after preparation and during five additional weeks of organ culture. RESULTS: Hemi-DMEK preparation was successful in all cases. All grafts formed a roll. A small area denuded of cells was observed after preparation along the straight edge of the DM roll. The mean ECD was 2654 (±65) cells/mm(2) before and 2651 (±94) cells/mm(2) immediately after hemi-DMEK preparation and declined gradually from 2518 (±133) cells/mm(2) after 1 week to 1847 (±170) cells/mm(2) after 5 weeks of organ-culture storage. DISCUSSION: Preparation of two hemi-DMEK grafts from one single human donor cornea is technically feasible, and the grafts can be stored after preparation in organ-culture similar to standard circular DMEK grafts. Hemi-DMEK may have the potential to double the availability of donor endothelial tissue for DMEK.

Bowman layer transplantation to reduce and stabilize progressive, advanced keratoconus.

OBJECTIVE: To evaluate the clinical outcome of mid-stromal isolated Bowman layer transplantation, a new surgical technique to reduce and stabilize ectasia in eyes with advanced keratoconus, to postpone penetrating keratoplasty or deep anterior lamellar keratoplasty, and to enable continued daily contact lens wear. DESIGN: Prospective, nonrandomized cohort study at a tertiary referral center. PARTICIPANTS: Twenty-two eyes of 19 patients with progressive, advanced keratoconus not eligible for ultraviolet cross-linking. INTERVENTIONS: The mid-stroma was manually dissected and an isolated donor Bowman layer was positioned within the stromal pocket. MAIN OUTCOME MEASURES: Before and up to 36 months after surgery (mean follow-up, 21±7 months), best spectacle-corrected visual acuity (BSCVA), best contact lens-corrected visual acuity (BCLVA), Scheimpflug-based corneal tomography measurements, endothelial cell density, biomicroscopy, refraction, and intraoperative and postoperative complications were recorded. RESULTS: Two surgeries were complicated by an intraoperative perforation of Descemet membrane; no other intraoperative or postoperative complications were observed. Maximum keratometry decreased on average from 77.2±6.2 diopters (D) to 69.2±3.7 D (P < 0.001) at 1 month after surgery and remained stable thereafter (P ≥ 0.072). Mean BSCVA improved from 1.27±0.44 logarithm of the minimum angle of resolution units before surgery to 0.90±0.30 logarithm of the minimum angle of resolution units 12 months after surgery (P < 0.001), whereas BCLVA remained stable (P = 0.105). Mean thinnest-point pachymetry increased from 332±59 µm before surgery to 360±50 µm at the latest follow-up (P = 0.012), and no change in endothelial cell density was found (P = 0.355). CONCLUSIONS: With isolated Bowman layer transplantation, reduction and stabilization of corneal ectasia was achieved in eyes with progressive, advanced keratoconus. Given the low risk for complications, the procedure may be performed to postpone penetrating or deep anterior lamellar keratoplasty.

Dehydration of corneal anterior donor tissue with polyethylene glycol (PEG)-enriched media.

Anterior donor grafts (including scleral rim, without Descemet membrane) increase in thickness and become hazy upon storage in organ culture (OC) medium. Transfer of these grafts to standard dehydration media just before transplantation does not reduce their thickness to normal. Therefore, we assessed the efficacy of different media enriched with polyethylene glycol (PEG) as dehydrating agents for organ-cultured anterior donor grafts. Grafts were harvested and stored in the commercial OC medium 'Max' (without dextran) for 1 week, and subsequently dehydrated in the standard commercial dehydration medium 'Jet' (with dextran) supplemented with 4-20% PEG3350, or 'Max' supplemented with 20% PEG6000 and PEG20.000, or 5-20% PEG35.000. Central corneal thickness (CCT), as assessed by anterior segment-optical coherence tomography, and transparency were evaluated before, and at 1, 4 and 7 days of dehydration. Transfer of grafts after 1 week of OC (average 1,200 µm) to 'Jet' supplemented with PEG3350 revealed a concentration-dependent effect of dehydration; CCT was restored to normal (500-600 µm) when 10% PEG3350 was added. However, transparency was only temporarily restored; after 1 day, the grafts turned hazy. In contrast, grafts transferred to 'Max' supplemented with 20% PEG35.000 were transparent throughout the evaluation period, but were dehydrated to beyond normal levels (average 300 µm). 'Max' supplemented with 5% PEG35.000 dehydrated grafts to normal values and restored transparency throughout. Thus, dehydration of anterior donor grafts prior to surgery in dextran-free OC medium supplemented with 5% PEG35.000 reduces graft thickness to normal and may facilitate anterior keratoplasty procedures.

Midstromal isolated Bowman layer graft for reduction of advanced keratoconus: a technique to postpone penetrating or deep anterior lamellar keratoplasty.

Midstromal implant of an isolated Bowman layer graft is a new approach to reduce ectasia in eyes with advanced keratoconus. The procedure should postpone penetrating or deep anterior lamellar keratoplasty. Ten eyes of 9 patients with progressive, advanced keratoconus and contact lens intolerance underwent the procedure with no intraoperative adverse events. Throughout the study period, we observed no complications related to stromal dissection and/or the Bowman layer graft. Maximum corneal power decreased from a mean (SD) of 74.5 (7.1) diopters (D) before to 68.3 (5.6) D after surgery (P = .002). Hence, implant of an isolated Bowman layer graft may offer a safe and effective new technique to reduce ectasia in eyes with advanced keratoconus, potentially allowing continued long-term contact lens wear. The low risk of complications may render the procedure suitable as a treatment to postpone penetrating or deep anterior lamellar keratoplasty in cases with impending contact lens intolerance and/or corneal scarring (clinicaltrials.gov Identifier: NCT01686906).

Are polymegethism, pleomorphism, and "poor swelling" valid discard parameters in immediate postmortem evaluation of human donor corneal endothelium?

PURPOSE: To study the validity of endothelial polymegethism, pleomorphism, and "poor swelling" as tissue discard parameters in the immediate postmortem evaluation of human donor corneal endothelium. METHODS: We retrospectively evaluated the quality of the endothelium at first and second evaluations for all processed corneas exhibiting moderate polymegethism, pleomorphism, or "poor swelling" in our eye bank over a 5-year period. RESULTS: Out of 2008 eyes qualifying for our study, 422 corneas (21%) showed polymegethism, pleomorphism, or poor swelling at the first tissue evaluation immediately after excision of the corneoscleral button. In 363 (86%) of these corneas, a normal endothelial mosaic was observed at the second tissue evaluation after 7 to 21 days of organ culture, whereas only 59 (14%) still showed persistent polymegethism, pleomorphism, or "poor swelling" at that time point. CONCLUSIONS: A recovery of normal endothelial cell mosaic and "normal swelling" at the second evaluation suggests that cellular contour parameters do not relate to tissue viability, but rather to a cellular stress reaction. If so, the validity of endothelial cellular contour morphology as an early parameter in assessing the suitability of a donor cornea for transplantation may be reconsidered.

Standardized 'no-touch' donor tissue preparation for DALK and DMEK: harvesting undamaged anterior and posterior transplants from the same donor cornea.

PURPOSE: To describe a standardized 'no-touch' harvesting technique of anterior and Descemet membrane (DM) grafts for use in deep anterior lamellar keratoplasty (DALK) and Descemet membrane endothelial keratoplasty (DMEK), which provides undamaged anterior and posterior corneal grafts. METHODS: A retrospective evaluation was performed of our standard method for harvesting DM grafts and DALK grafts (Technique I; n = 31) versus a newly designed 'no-touch' technique (Technique II; n = 31), in which a peripheral ring of trabecular meshwork tissue is left in-situ, and the DM graft is trephined on an underlying soft contact lens. Endothelial cell density (ECD) before and immediately after DM stripping was used as the main outcome parameter. RESULTS: Endothelial cell density did not differ within Techniques I and II (before versus after DM stripping) (p = 0.75 and p = 0.54, respectively) or among Techniques I and II (p = 0.61). With the latter technique, anterior corneal grafts and posterior DM grafts could be harvested with negligible damage to the endothelial cell layer or the posterior stromal bed. All 93 grafts (62 DM grafts) were eligible for transplantation, and six months post-operatively all transplants used were functional. CONCLUSION: The new technique offers the following advantages: (i) production of 'undamaged' grafts for DALK and DMEK, (ii) better controlled tissue handling of the thin DM graft during DM stripping and (iii) an increase in availability of corneal grafts obtained from the same donor tissue pool.