The aim of this study was to analyze Descemet stripping automated endothelial keratoplasty donor endothelial grafts, prepared by using a microkeratome, in terms of uniformity, circularity, and concentricity.
In this pilot study, 12 human donor corneas were prepared by means of a microkeratome and imaged using the Visante anterior segment optical coherence tomography along 4 meridians. The microkeratome enters and exits the corneal tissue at an angle, creating a donor graft bed with a uniform stromal (US) thickness in between the angled edges. We termed the angled portion the “nonuniform stromal transitional annulus” (STA), the point of entry and exit of the microkeratome the “epithelium-to-epithelium” (E-E) diameter, and the length of the US bed the “US” diameter. The E-E and US diameters were measured to create a model of each donor graft, from which circularity and concentricity were calculated. The STA length and height were measured, and the slope was calculated.
The mean E-E diameter was 10.69 ± 0.32 mm (range, 9.46–11.75 mm) and the mean US diameter was 8.96 ± 0.40 mm (range, 7.62–10.28 mm). The microkeratome generated elliptical rather than circular cuts, with a mean eccentricity of 0.34 ± 0.098 (range, 0.22–0.58). Eccentricity values between 0 and 1 represent ellipses, with zero characterizing a circle. The US ellipses and E-E ellipses were not concentric, with a mean deviation of the centers of the shapes of 177.06 ± 92.06 μm (range, 21.95–322.22 μm). The mean STA length was 0.73 ± 0.31 mm (range, 0.25–1.89 mm), the mean height was 0.43 ± 0.08 mm (range, 0.28–0.64 mm), and the mean slope was 34.11 ± 14.00° (range, 8.43–53.67°).
Microkeratome cuts created nonuniform, noncircular nonconcentric donor grafts. Asymmetry and nonuniformity of donor tissue may help explain suboptimal visual outcomes.