Predicting graft thickness in ultrathin DSAEK using a mechanical microkeratome system.

PURPOSE: To examine pre-cut factors associated with post-cut graft thickness in ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) prepared with a mechanical microkeratome system and to develop a nomogram to support blade selection. METHODS: Donor corneas processed at a single eye bank were included. All tissues were dissected using a standardised mechanical microkeratome protocol with fixed pressure and cutting speed. Pre-cut variables included central pachymetry, microkeratome blade size, endothelial cell density, cause of death and demographic characteristics. Multivariable regression was used to evaluate predictors of post-cut graft thickness. Adjusted predictions across the observed pachymetry range were generated to construct a nomogram estimating expected graft thickness for each blade. RESULTS: A total of 107 donor corneas were analysed. Mean post-cut graft thickness was 92.7±24.3 µm. In the multivariable model, blade size (p<0.001) and pre-cut pachymetry (p<0.001) showed the strongest associations with graft thickness, accounting together for approximately 45.7% of model variance. The cut-to-blade ratio analysis indicated that all blades produced cuts deeper than their nominal thickness, with ratios increasing across blade sizes. The resulting nomogram enables selection of the blade more likely to achieve grafts within the 70-100 µm range based on the donor's initial pachymetry. CONCLUSIONS: Blade size and initial pachymetry show measurable associations with post-cut graft thickness in UT-DSAEK prepared under standardised mechanical conditions. The proposed nomogram offers a practical tool to assist in selecting the blade expected to achieve ultrathin grafts with greater reproducibility.