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.

Bowman Layer Onlay Grafting as a Minimally Invasive Treatment for the Most Challenging Cases in Keratoconus.

PURPOSE: To analyze the clinical outcomes after Bowman layer (BL) onlay grafting for the treatment of progressive, advanced keratoconus. DESIGN: Prospective, interventional case series. METHODS: Twenty-one eyes underwent BL onlay grafting. After removing the epithelium, a single or double BL graft was "stretched" onto the corneal surface, allowed to dry-in, and a soft bandage lens was placed until the graft was re-epithelialized. Best spectacle- and/or best contact lens-corrected visual acuity (BSCVA/BCLVA), corneal tomography, and postoperative complication rates were analyzed for the total group and 2 subgroups (group 1: preoperative maximum keratometry [Kmax] <69 diopters [D; n = 7); group 2: preoperative Kmax ≥69 D [n = 14]). Follow-up ranged from 6 to 36 months (mean 21 ± 11 months). RESULTS: All 21 surgeries were uneventful. Overall, Kmax changed from 76 ± 12 D preoperatively to 72 ± 9 D at 6 to 36 months postoperatively (P = .015). Kmax decreased by 6 D in group 2 (P = .002) but did not change in group 1. Average BSCVA remained stable for group 1 and improved from preoperatively 0.8 ± 0.4 to 0.4 ± 0.2 logarithm of the minimum angle of resolution postoperatively in group 2 (P = .032); BCLVA remained stable (P > .05). Within the first postoperative weeks, 2 eyes required BL graft repositioning after inadvertent bandage lens removal and 4 eyes underwent BL retransplantation for incomplete re-epithelialization. One eye underwent BL regrafting 12 months postoperatively after traumatic corneal erosion. All eyes showed a completely re-epithelialized graft at the last available follow-up. CONCLUSIONS: BL onlay grafting is a completely extraocular, minimally invasive surgical technique, providing up to -6 D of corneal flattening in eyes with advanced progressive keratoconus, allowing for continued (scleral) contact lens wear and therefore preserving the BCLVA.

P19-A118†Bowman layer onlay: preparation and transplantation (BLOT).

PURPOSE: With the introduction of Bowman layer onlay transplantation (BLOT), the need for BL transplants increases.In this study, the clinical outcomes of BLOT are described and the results of three different BL graft preparation methods are evaluated: manually (m-BL), femtosecond laser-assisted (fs-BL), and femtosecond laser-assisted followed by excimer laser (fs/ex-BL). METHOD: Twenty-one eyes with advanced progressive keratoconus underwent BLOT with m-BL. Best spectacle- and/or best contact lens-corrected visual acuity (BSCVA/BCLVA), corneal tomography, and complications were recorded. Follow-up ranged from 6-36 months with a mean follow-up time of 21±12 months.To evaluate BL preparation methods, Descemet membrane-denuded donor corneas (n=41) were used (n=2 for m-BL, n=18 for fs-BL and n=21 for fs/ex-BL). For fs-BL, corneas were placed on an artificial anterior chamber and different depth cuts were performed with decreasing decrements starting from 30 µm (diameter 9.0 mm). For fs/ex-BL, a superficial flap of 80 µm was created by the femtosecond laser (FEMTO-LDV Z8, Ziemer). Followed by residual stroma ablation by excimer laser (Schwind Amaris 750S) with increasing increments. Grafts were analyzed visually, and graft thickness regularity was evaluated by histological analysis and Transmission Electron Microscopy (TEM). RESULTS: All twenty-one surgeries could be performed without intraoperative complications. Average maximum keratometry changed from 75.8±12D preoperatively to 72.2±9D at the last available follow-up (n=21, P<0.05), and BSCVA/BCLVA improved. Five patients required a regraft; four of those because of a graft detachment within one week.Evaluation of BL-preparation methods: Fs-BL preparation was successful until 14µm cuts (success rate: 12 out of 14, 86%). Fs/ex-BL graft preparation was most successful after an 80µm cut by femtosecond laser with subsequent 60µm ablation by excimer laser (success rate: 15 out of 21, 71%). After the femtosecond laser cut, traces of the femtosecond laser treatment were visible on the flap. While m-BL showed long protruding stromal fibers, they were shorter in fs-BL and absent in fs/ex-BL. CONCLUSION: BL-onlay grafting may be a feasible surgical technique, providing on average -3D of corneal flattening in eyes with advanced progressive keratoconus, while improving patient's visual acuity.Fs-BL and fs/ex-BL preparation may be faster alternatives to manual BL graft preparation.

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.

Endothelial Cell Viability after DMEK Graft Preparation.

Aim: To evaluate the effect of graft preparation and organ-culture storage on endothelial cell density (ECD) and viability of Descemet membrane endothelial keratoplasty (DMEK) grafts.Materials and methods: DMEK grafts (n = 27) were prepared at Amnitrans EyeBank Rotterdam from 27 corneas (15 donors) that were eligible for transplantation but could not be allocated due to the Covid-19-related cancellation of elective surgeries. Cell viability (by Calcein-AM staining) and ECD of five grafts originally scheduled for transplantation were evaluated on the originally planned surgery day, whereas 22 grafts from paired donor corneas were evaluated either directly post-preparation or after 3-7 days of storage. ECD was analyzed by light microscopy (LM ECD) and Calcein-AM staining (Calcein-ECD).Results: Light microscopy (LM) evaluation of all grafts showed an unremarkable endothelial cell monolayer directly after preparation. However, median Calcein-ECD for the five grafts initially allocated for transplantation was 18% (range 92-73%) lower than median LM ECD. For the paired DMEK grafts, Calcein-ECD determined by Calcein-AM staining on the day of graft preparation and after 3-7 days of graft storage showed a median decrease of 1% and 2%, respectively. Median percentage of central graft area populated by viable cells after preparation and after 3-7 days of graft storage was 88% and 92%, respectively.Conclusion: Cell viability of most of the grafts will not be affected by preparation and storage. Endothelial cell damage may be observed for some grafts within hours after preparation, with insignificant additional ECD changes during 3-7 days of graft storage. Implementing an additional post-preparation step in the eye bank to evaluate cell density before graft release for transplantation may help to reduce postoperative DMEK complications.

Bowman Layer Onlay Grafting: Proof-of-Concept of a New Technique to Flatten Corneal Curvature and Reduce Progression in Keratoconus.

PURPOSE: The aim of this study was to describe a new surgical technique for flattening the corneal curvature and to reduce progression in eyes with advanced progressive keratoconus (KC) by using Bowman layer (BL) onlay grafting and to report on the preliminary outcomes of this procedure. METHODS: In this prospective interventional case series, 5 patients with advanced progressive KC underwent BL onlay grafting. After removal of the epithelium, a BL graft was placed and "stretched" onto the stroma, and a bandage lens was placed to cover the BL graft. In 1 case, BL onlay grafting could be performed immediately after ultraviolet corneal crosslinking; all other eyes were ineligible for ultraviolet corneal crosslinking. Best spectacle- and/or best contact lens-corrected visual acuity, refraction, biomicroscopy, corneal tomography, anterior segment optical coherence tomography, and complications were recorded at 1 week and at 1, 3, 6, 9, and 12 to 15 months postoperatively. RESULTS: All 5 surgeries could be performed successfully. Average maximum keratometry went from 75 diopters (D) preoperatively to 70 D at 1 year postoperatively. All eyes showed a completely reepithelialized and a well-integrated graft. Best spectacle-corrected visual acuity improved at least 2 Snellen lines (or more) in 3 of 5 cases and best contact lens-corrected visual acuity remained stable, improving by 3 Snellen lines in case 1 at 15 months postoperatively. Satisfaction was high, and all eyes again had full contact lens tolerance. CONCLUSIONS: BL onlay grafting may be a feasible surgical technique, providing up to -5 D of corneal flattening in eyes with advanced KC.

Bowman Layer Onlay Transplantation to Manage Herpes Corneal Scar.

PURPOSE: To introduce the concept of using a Bowman layer (BL) onlay graft to manage superficial herpetic corneal scarring and to describe the clinical outcomes of the first 2 cases undergoing this procedure. METHODS: Two patients with a quiescent superficial corneal scar after herpes (varicella zoster virus [n = 1] and herpes simplex virus [n = 1]) keratitis underwent BL onlay transplantation. After the removal of the host epithelium and limited superficial keratectomy, an isolated BL graft was placed onto the host corneal surface. The cornea was then covered with an amniotic membrane and a bandage contact lens. Best spectacle-corrected visual acuity (VA) and/or best contact lens-corrected VA (BCLVA), biomicroscopy, corneal tomography, and anterior segment optical coherence tomography were recorded at 1 week, 1 month, and 3, 6, 9, 12, and 18 months postoperatively. RESULTS: In both cases, the surgical and postoperative courses were uneventful. An improvement of the corneal clarity was observed at biomicroscopy, and no varicella zoster virus/herpes simplex virus reactivation occurred throughout the follow-up period. Biomicroscopy, Scheimpflug imaging, and anterior segment optical coherence tomography showed a completely epithelialized and well-integrated graft postoperatively. In case 1, BCLVA with a scleral lens improved from 20/100 (0.1) preoperatively to 20/32 (0.6) postoperatively. For case 2, no preoperative BCLVA was available, but a BCLVA of 20/36 (0.55) was achieved after the procedure. CONCLUSIONS: A BL onlay graft may be a feasible surgical procedure, which may have the potential to reduce superficial corneal scarring and/or anterior corneal irregularities without resorting to deeper keratoplasty in these complex cases.

Bowman layer transplantation: 5-year results.

PURPOSE: The purpose of this study was to evaluate the 5-year clinical results of isolated Bowman layer (BL) transplantation in the treatment of advanced keratoconus. METHODS: In this prospective, single-center, interventional case series at a tertiary referral center, 20 eyes of 17 patients with advanced keratoconus underwent BL transplantation, i.e. an isolated Bowman layer graft was positioned into a manually dissected mid-stromal pocket. Scheimpflug-based corneal tomography measurements, best corrected spectacle and contact lens visual acuities (BSCVA and BCLVA), endothelial cell density, and complications were evaluated up to 5 years after surgery. RESULTS: Measured simulated and maximum keratometry (Kmean and Kmax) values were stable up to 5 years after surgery (P = .310 and P = .195 for 5 years compared to 1 month follow-up, respectively), following an initial decrease from pre- to 1 month postoperatively (P < .001 each). Mean LogMAR BSCVA remained stable (P > .99), after an initial improvement from pre- to 12 months postoperatively (P = .007). Mean BCLVA did not change from preoperative to 5 years postoperatively (P = .219). During all postoperative follow-ups, mean densitometry values were higher than preoperatively (P < .001). A corneal hydrops occurred in one eye at 4.5 years postoperatively; no other postoperative complications were observed. Kaplan-Meier analysis showed an estimated success rate of 84% at 5 years postoperatively. Endothelial cell density remained stable from before to 5 years after surgery (P = .319). CONCLUSIONS: After early postoperative corneal flattening, topographies were stable up to 5 years after BL transplantation, preserving BCLVA and contact lens tolerance, potentially allowing long term postponement of penetrating or deep anterior lamellar keratoplasty.

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.

Technical feasibility of isolated Bowman layer graft preparation by femtosecond laser: a pilot study.

PURPOSE: To evaluate the technical feasibility of isolated Bowman layer (BL) graft preparation by femtosecond laser (FSL) and to compare the ultrastructural morphology to manually dissected grafts. METHODS: Five whole globes were placed in custom-made eye holders and debrided of epithelium. After programming a dissection depth of 20 µm, the FSL was docked into position and 5 isolated BL grafts were created. From 5 additional globes, corneoscleral buttons were procured, mounted in artificial anterior chambers, and stripped of BL via the previously described manual technique. Three specimens from both series were randomly selected and assigned to transmission electron microscopy for ultrastructural evaluation and thickness measurements. RESULTS: All dissections were uneventful and 10 total grafts were produced: 5 by FSL and 5 by manual dissection. Mean graft thickness was 37 (±8.6) µm (n = 3) for the FSL group and 11.7 (±1.6) µm (n = 3) for the manually dissected group. Transmission electron microscopy revealed a thick but relatively smooth posterior cut edge in the FSL group, versus a virtually isolated BL with irregular rests of dispersed stroma in the manually dissected group. CONCLUSIONS: Femtosecond laser may have potential for harvesting intact BL and with a smooth posterior surface, but accompanied by variable amounts of anterior stroma owing to technical limitations.

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.

Association Between Graft Storage Time and Donor Age With Endothelial Cell Density and Graft Adherence After Descemet Membrane Endothelial Keratoplasty.

IMPORTANCE: After retrospectively evaluating the clinical outcome of 500 consecutive cases after Descemet membrane endothelial keratoplasty (DMEK), we extended the analysis in this study by assessing the effect of donor-related parameters on endothelial cell density (ECD) decline and detachment rate in this group. OBSERVATIONS: This retrospective case series included 500 cases who had undergone DMEK from October 2007 to September 2012 at the Netherlands Institute for Innovative Ocular Surgery (NIIOS), Rotterdam, the Netherlands. Logistic regression analysis (n = 332 eyes) showed that donor age might be associated with a 3% increase in the risk for a detachment (odds ratio, 0.97; 95% CI, 0.94-1.00; P = .049) (ie, higher donor age seems to be associated with lower chances of a detachment). In addition, linear regression analysis indicated that graft storage time in medium was associated with ECD decrease (ie, the longer the storage time, the larger the decrease at 6 months after DMEK) (P = .01). CONCLUSIONS AND RELEVANCE: We showed an association between graft storage time and ECD decline after DMEK and possibly between donor age and graft detachment. Therefore, donor storage times should be kept as short as possible to improve short-term ECDs. More research is needed to draw definite conclusions on the possible effect of donor age on the chance of a detachment after DMEK.

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.