BASIC INVESTIGATION Effect of Microkeratome Pass on Tissue Processing for Descemet Stripping Automated Endothelial Keratoplasty Maria A. Woodward, MD,* Michael S. Titus, CEBT,† and Roni M. Shtein, MD, MS* Purpose: The aim of this study was to optimize tissue preparation for Descemet stripping automated endothelial keratoplasty (DSAEK) by evaluating the outcomes of corneal tissue processing. Methods: Forty-five corneas underwent microkeratome (MK) tissue processing for single-cut DSAEK, and 74 corneas were processed for double-cut (ultrathin) DSAEK. For single-cut process- ing, the corneas were cut at the thickest peripheral point (method A) or at a random location (method B). For double-cut processing, tissues were cut at the thickest peripheral point and then 180 degrees away (method C), at the thickest point and then the second thickest point (method D), or at a random peripheral starting point and then 180 degrees away (method E). The tissue was measured for corneal thickness and for endothelial cell density. Results: For single-cut DSAEK tissues, there was no difference in the central tissue thickness (P = 0.23), mean peripheral thickness (P = 0.57), or peripheral tissue symmetry (P = 0.27) between A and B measured by anterior segment optical coherence tomography. For double-cut (ultrathin) DSAEK tissues, tissues cut using method C or D were not statistically significantly different for perforation rate, final central corneal thickness, mean peripheral thickness, or for tissue symmetry (P = 0.57, P = 0.33, P = 0.63, P = 0.48, respec- tively). All 4 tissues cut using method E were perforated during the second MK pass. The perforation, or donor loss rate, for ultrathin cut tissue preparation in group C was 23%, and for group D, it was 29%. Only 65% of successfully cut tissues in groups C and D actually achieved a thickness of #100 mm. Conclusions: Single-cut DSAEK tissue processing can be per- formed safely without peripheral corneal thickness measurements. Ultrathin DSAEK tissue processing requires peripheral thickness measurements for the first, but not for the second MK pass. Ultrathin DSAEK tissue processing led to high perforation rates. Certain tissue characteristics, processing techniques, and MK head size play a role in successful donor corneal tissue processing of ultrathin DSAEK tissue. Key Words: corneal transplantation, endothelial keratoplasty, tissue processing, instrumentation (Cornea 2014;33:507–509) E ndothelial keratoplasty (EK) was introduced in 1998 by Melles et al, 1 refined by Gorovoy 2 in the United States, and it has become the principal method of surgical treatment for corneal endothelial disorders including Fuchs dystrophy. EK accounts for 52% of all US corneal transplants performed in 2012. 3,4 Surgeons pursue variations in EK techniques to improve visual outcomes and rapidity of visual recovery. 5 Interface architecture, graft shape, and interface haze affect visual outcomes; however, the impact of graft thickness has been debated. 6–10 Descemet stripping automated EK (DSAEK) currently remains the most commonly performed procedure for EK. 11 Advocates of ultrathin DSAEK (defined here as ,100-mm graft thickness) hope that thinner tissue will improve visual outcomes. This article describes a series of experiments aimed at optimizing ultrathin DSAEK tissue processing using the double-pass technique. METHODS One hundred nineteen human corneas were procured uniformly according to the Midwest Eye-Banks procedures using an in situ excision technique and were placed in Optisol storage medium (Bausch & Lomb, Rochester, NY). All cor- neas met the endothelial cell density and slit-lamp criteria laid down by eye banking standards 12 with the caveat that death- to-processing time was extended to 14 days. Forty-five corneas were analyzed after single-cut DSAEK processing, and 74 corneas were analyzed after double-cut DSAEK tissue processing. Single-cut donor corneas underwent standard microkeratome (MK) tissue processing on an artificial anterior chamber (Moria, Doylestown, PA). 13 The MK head size was selected as follows: for tissues ,600 mm, the cutting head depth was 300 mm, and for tissues $600 mm, the cutting head depth was 350 mm. For single-cut processing, 26 corneas were cut at the thickest peripheral point (processing method A), and 19 eyes were cut at a random location (pro- cessing method B). For ultrathin tissue processing, the corneas were mounted on an artificial anterior chamber (Moria, Doyles- town, PA) filled with balanced salt solution. We used a modified version of the single-pass Moria device designed for double pass before the existence of disposable kits. The Received for publication November 21, 2013; revision received December 30, 2013; accepted January 14, 2014. Published online ahead of print March 11, 2014. From the *Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI; and †Heartlands Lions Eye Bank, Kansas City, MO. M. A. Woodward received a grant from Midwest Eye-Banks to support this research. M.S. Titus is an employee of the Heartlands Lions Eye Institute. The authors have no other conflicts of interest to disclose. Reprints: Maria A. Woodward, Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan, 1000 Wall St, Ann Arbor, MI 48105 (e-mail: mariawoo@umich.edu). Copyright © 2014 by Lippincott Williams & Wilkins Cornea  Volume 33, Number 5, May 2014 www.corneajrnl.com | 507