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.

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.

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.