Graft profile and thickness as a function of cut transition speed in Descemet-stripping automated endothelial keratoplasty

Abstract

To determine the profile of endothelial keratoplasty lenticules prepared using a microkeratome and evaluate the impact of varying cut transition speed on cut depth and profile using anterior segment optical coherence tomography (AS-OCT). Department of Cornea and External Diseases, Moorfields Eye Hospital, London. United Kingdom. Experimental study. Fourier-domain AS-OCT was used to image 25 corneal specimens before and after microkeratome dissection with a 350 μm head. A pilot series of 7 corneas were cut and imaged with the following 18 corneas divided into regular cut transition speed and slow cut transition speed groups (9 in each). Proximal, central, and distal precut corneal thickness and post-cut residual bed thickness were measured using the integrated caliper tools of the Fourier-domain AS-OCT device. Cut depth was calculated by subtraction. The slower microkeratome pass speed produced significantly thinner donor lenticules (mean 148 ± 45 μm [SD]) than the standard pass speed (mean 234 ± 35 μm) (P ≤.0001). In both groups, significant asymmetry was observed in donor lenticules with a deeper cut depth and a thinner lenticule at the beginning of the microkeratome pass (proximal stromal bed). The mean difference between the proximal and distal stromal bed thickness was 61 ± 63 μm in the standard group and 52 ± 22 μm in the slow-pass group (P=.159). Reducing the transition speed in microkeratome dissection produced thinner donor lenticules. Thickness asymmetry is an inherent flaw with current microkeratome dissection that cannot be easily corrected by altering preparation technique.