Preloaded DMEK with endo-in technique: Standardizing and minimizing the learning curve over 5 years using 599 corneal tissues.

PURPOSE: To report the outcomes of standardizing pre-loaded DMEK with endothelium-inwards and its associated learning curve. METHODS: Between 2017 and 2021, a total of 599 tissues were stripped using 'trephine and strip' method and loaded by folding the tissue as a taco-fold with endothelium-inwards. The folded tissues were pulled inside the funnel of a 2.2 mm IOL cartridge and stored for the desired number of days in organ culture media supplemented with dextran. Donor characteristics, endothelial cell loss (ECL) and mortality assessed by trypan blue positivity before and after stripping, and eventful cases during stripping/loading were recorded. RESULTS: The tissues found unsuitable for transplant after stripping (6.7%) were significantly higher compared with loading (0.67%). Central or peripheral tears, fragility of the tissues, and insufficient endothelial cell density mainly attributed towards the discard rate. Mean ECL from pre-stripping to post-stripping was 0.27% with endothelial cell mortality of 0.64% at the end of stripping. Cumulative endothelial mortality fold change (pre-strip to post-strip) was high in the first two years of operation (18.9%), which reduced to 5.1% in the following three years with significant difference (p = 0.0352). Average tissue wastage (3 operators) from first 1-150 tissues was 3%, which significantly reduced to 0.9% after achieving the learning curve (151-250) (p = 0.0492). CONCLUSION: DMEK graft preparation requires a learning curve. However, an operator with DMEK stripping skills can easily adapt to pre-loading a DMEK graft in endothelium-inwards fashion with minimal learning curve.

Eye Bank Management of Irregular Descemet Stripping Automated Endothelial Keratoplasty Lenticules.

PURPOSE: To report the management of precut Descemet stripping automated endothelial keratoplasty (DSAEK) lenticules unsuitable for transplantation because of irregular anterior profile after microkeratome cutting. METHODS: After preparation for DSAEK, 20 tissues were considered unsuitable for transplantation because of nonhomogeneous posterior stromal thickness. To convert them into suitable tissues for surgery, manual stromal delamination was performed by removing the excess stromal layers after the indications obtained through optical coherence tomography. These tissues were further transplanted as ultrathin DSAEK. RESULTS: Nineteen tissues were delaminated successfully. The average reduction in thickness in the center (63 ± 69 µm; P = 0.0101) and periphery (129 ± 39 µm; P < 0.0001) before and after delamination was significantly different. One tissue showed signs of perforation during manual dissection and therefore considered unsuitable for transplantation. Primary graft failure was reported in one case, but it was not correlated with the tissue preparation. No other clinical complications were observed after surgery. CONCLUSIONS: Manual delamination of the stroma because of irregular microkeratome cutting is a viable option to obtain a uniform graft thickness required for DSAEK surgeries. This technique can further reduce tissue wastage that is observed after microkeratome cutting errors.

Descemet Membrane Endothelial Keratoplasty Learning Curve for Graft Preparation in an Eye Bank Using 645 Donor Corneas.

PURPOSE: To investigate the learning curve of Descemet membrane endothelial keratoplasty (DMEK) graft preparation in an eye bank. METHODS: Four operators prepared 645 DMEK grafts using the stripping technique between 2014 and 2017 at the Veneto Eye Bank Foundation, Italy. Endothelial cell loss (ECL) and tissue wastage were recorded retrospectively after DMEK preparation and correlated with the number of tissues prepared each year by each operator. On average, our operators performed 1 donor preparation a week over the course of this study. Only donors older than 60 years were used in this study, and approximately 10% of donors had diabetes. The Wilcoxon test for paired data and 1-way ANOVA were used for checking statistical significance with the Tukey test as post hoc analysis. P < 0.05 was considered statistically significant. RESULTS: ECL did not change significantly over time from operator 1. Significant ECL drop was noted from operator 2 between years 2014-2016 (P = 0.0049) and 2017 (P = 0.0094); from operator 3 between years 2015-2016 (P = 0.0288) and 2017 (P = 0.0097); and from operator 4 between 2015-2016 (P = 0.0469) and 2017 (P = 0.0331). Operators 1 and 3 did not show a significant difference, considering every 50 grafts prepared by each operator. Operator 2 showed significant ECL drop between 1 to 50 and 51 to 100 (P = 0.0002) and 1 to 50 and 101 to 150 (P = 0.0001) grafts. Operator 4 showed significant ECL drop between 1 to 50 and 101 to 150 (P = 0.002) and 51 to 100 and 101 to 141 (P = 0.0207) grafts. No intraoperator difference was observed per 50 grafts (P > 0.05). CONCLUSIONS: There is a learning curve for DMEK graft preparation. ECL and tissue wastage can be reduced with practice and skills. However, each operator may be limited to his or her own learning capability.

Standardizing Descemet Membrane Endothelial Keratoplasty Graft Preparation Method in the Eye Bank-Experience of 527 Descemet Membrane Endothelial Keratoplasty Tissues.

PURPOSE: To share the experience and provide a standardized protocol for Descemet membrane endothelial keratoplasty (DMEK) graft preparation. METHODS: A retrospective study based on 527 prestripped DMEK tissues that were prepared between 2014 and 2017. The experience of using different instruments and techniques has been described, and a standardized technique for preparing DMEK grafts has been identified. The tissues in general were prepared by superficially tapping the endothelial side with a Moria trephine (9.5 mm diameter). The plane of cleavage was identified using a cleavage hook, and the DMEK graft was deadhered from the trephined site throughout the circumference for ease of excising the graft. The DMEK graft was peeled using either one or multiple quadrant methods depending on the challenges faced during excision. The graft was finally marked with the letter "F" to identify the orientation during surgery. Data on endothelial cell loss (ECL) and challenging cases were observed, monitored, and recorded during this period. RESULTS: Less than 1 percent trypan blue-positive cells with tissue wastage of <6% was observed during the study period. Our standardized stripping technique has resulted in an overall ECL of 4.6%. Marking Descemet membrane showed 0.5% cell mortality. CONCLUSIONS: Standardizing DMEK technique using specific tools and simple techniques would help new surgeons to decide the instruments and improve their tissue preparation skills also in challenging cases such as previous cataract incisions or horseshoe-shaped tears, further reducing ECL or tissue wastage.

Improved preparation and preservation of human keratoplasty lenticules.

PURPOSE: To improve the preparation of lenticules from human cornea and to obtain their preservation without loss of viable keratocytes. METHODS: The epithelium was manually removed after bathing the surface of the cornea with a solution of trypsin and EDTA. Lenticules were prepared by microkeratome resection and viable keratocytes were visualized by staining with thiazolyl blue (MTT). RESULTS: The pretreatment with trypsin-EDTA allowed the removal of the epithelium without damage to the keratocytes and the stroma. When these lenticules were incubated in Optisol-GS for 7 days at 4 degrees C, they showed a limited thickness increase and a preservation of keratocyte viability. CONCLUSION: This procedure allows the preparation of lenticules with viable keratocytes that can be preserved in the cold for at least 1 week.