Chamber shallowing technique for challenging DMEK cases: Tucking cellulose spears under the speculum to augment posterior pressure.

Some anterior chambers do not readily shallow because of insufficient posterior pressure and/or very deep anterior chamber anatomy, which can make unscrolling descemet membrane endothelial keratoplasty (DMEK) tissue more challenging with an unmodified tap technique. We present a hands-free method for augmenting posterior pressure by temporarily tucking cellulose sponges under the blades of the eyelid speculum. The sponges transfer some of the eyelid speculum's weight onto the bulbar surface posterior to the iris, thereby indenting the sclera and causing the iris diaphragm to bulge further forward. This hands-free technique can transform a potentially challenging DMEK case into a more straightforward one by facilitating both a shallow anterior chamber and a bimanual unscrolling technique. However, it only works in bicameral eyes with a vitreous body (e.g., an eye with penetrating keratoplasty, vitreous syneresis, and axial myopia) and will not work in unicameral eyes after vitrectomy (e.g., an eye with an Anterior Chamber Intraocular Lens (ACIOL)).

Deformable Biomechanics of DMEK Tissue Scrolls Traveling Through Narrow Lumens: The Inverse Relationships Between Fluid Velocity, Scroll Width, and Wall Contact and Their Clinical Implications for Preloading.

PURPOSE: The aim of this study was to evaluate Descemet membrane endothelial keratoplasty (DMEK) scroll width and length in relation to variable velocities as the tissue transits through wide and narrow lumen glass tubes. METHODS: Sets of DMEK tissue were processed using the Iowa Lions Eye Bank standard DMEK protocol and were passed through 2 glass tube widths at variable speeds. Two hourglass-shaped glass tubes were created, one "wide" and one "narrow." A syringe pump, valve, and pressure gauge were used to modulate tissue speed through each tube. For both tube sizes, DMEK tissue was passed through their lumens with incrementally increasing velocity and visualized with a high-speed camera at frame rates from 1000 to 8000 fps. Scroll width and length were measured using IDT Motion Studio software and digital calipers. RESULTS: There was a significant, indirect correlation between scroll velocity and width in both the wide (R2 = -0.98, P < 0.001) and narrow (R2 = -0.84, P < 0.001) tubes. There was a significant, direct correlation between scroll velocity and length in both the wide (R2 = 0.84, P < 0.001) and narrow (R2 = 0.83, P < 0.001) tubes. The resting widths of the scrolls were 105% and 207% wider than the wide and narrow tubes, respectively. All transits recorded scroll widths that were equal to or smaller than their respective tube's internal diameter. CONCLUSIONS: There is a significant, inverse correlation between DMEK scroll velocity and width as well as a direct correlation between scroll velocity and length, allowing DMEK scrolls to transit through a tube that is narrower than its resting width without sustained lumen wall contact.

Using a Cone-Shaped Glass Funnel Adapter Reduces Endothelial Cell Loss Caused by Preloading Descemet Membrane Endothelial Keratoplasty Tissue.

PURPOSE: The aims of this study were 1) to compare "front" and "rear" methods for loading Descemet membrane endothelial keratoplasty (DMEK) tissue into both micro-Jones and standard-Jones tubes and 2) to evaluate the efficacy of a cone-shaped glass funnel adapter designed to make loading DMEK tissue safer for corneal endothelial cells. METHODS: The corneal endothelium was stained with 0.06% trypan blue to confirm equivalence between mate corneas. The tissues were then processed using the Iowa Lions Eye Bank standard DMEK protocol. In comparison 1, one mate was loaded into the rear of a micro-Jones or standard-Jones tube and the other was loaded into the front of the same tube. In comparison 2, one mate was loaded into the front of the micro-Jones tube and the other was loaded through the cone-shaped funnel adapter into the rear. All tissues were ejected through the front of the modified Jones tubes and assessed for endothelial cell loss (ECL) with calcein AM staining, FIJI, and Trainable Weka Segmentation; scroll widths were measured digitally. RESULTS: There were no statistically significant differences in ECL between front and rear loading [micro (N = 6 pairs): front 15.74% vs. rear 17.95%; standard (N = 6 pairs): front 19.58% vs. rear 19.17%; all P > 0.05]. DMEK scrolls loaded with the funnel adapter exhibited lower ECL compared with scrolls loaded through the front [micro (N = 8 pairs): front 13.53% vs. loading funnel 2.40%; P < 0.001]. Loading with the adapter was not faster (front 6.66 seconds vs. loading funnel 5.52 seconds; P = 0.24). CONCLUSIONS: Using a cone-shaped DMEK loading funnel may reduce ECL sustained during preloading.