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.

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.

17†Cell viability after DMEK preparation.

PURPOSE: 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. 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 5 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 5 grafts initially allocated for transplantation was 18% (range 9-73%) 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. CONCLUSIONS: 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.

37†Descemet membrane endothelial keratoplasty (DMEK): 10-year clinical outcomes and graft survival.

PURPOSE: To evaluate graft survival and clinical outcomes up to 10 years after Descemet membrane endothelial keratoplasty (DMEK). SETTING/VENUE: Retrospective cohort study conducted at the Netherlands Institute for Innovative Ocular Surgery. METHODS: 750 consecutive DMEK eyes, not including the very first 25 DMEK eyes that constitute the technique learning curve, were included. Main outcome parameters (survival, best-corrected visual acuity (BCVA), central endothelial cell density (ECD)) was evaluated up to 10-years postoperatively and postoperative complications were documented. Outcomes were analyzed for the entire study group and separately for the subgroup of the first 100 DMEK eyes. RESULTS: For the subgroup of 100 DMEK eyes, 82% and 89% reached a BCVA of ≥20/25 (Decimal VA ≥0.8) at 5- and 10 years postoperatively, respectively, and preoperative donor ECD decreased by 59% at 5 years and 68% at 10 years postoperatively. Graft survival probability for the first 100 DMEK eyes was 0.83 [95% Confidence Interval (CI), 0.75-0.92] and 0.79 [95% CI, 0.70 -0.88] at 5- and 10-years postoperatively, respectively. For the total study group, clinical outcome in terms of BCVA and ECD were comparable, but graft survival probability was significantly higher at 5- and 10-year postoperatively. CONCLUSIONS: Most eyes operated in the pioneering phase of DMEK showed excellent and stable clinical outcomes with a promising graft longevity over the first decade after surgery. The increase in DMEK experience resulted in a lower graft failure rate and positively affected longer-term graft survival probability.