Corneal grafts from 47 failed DSAEK cases in 42 patients who subsequently underwent PK or repeated DSAEK were obtained between January 1, 2007, and December 31, 2009, in the L. F. Montgomery Ophthalmic Pathology Laboratory, Emory University, Atlanta, Georgia. The specimens were routinely processed for light microscopic examination by fixation with formalin, 10%, dehydration in increasing grades of alcohol, xylene clearing, paraffin embedding, sectioning at 7-μm thickness, and staining with hematoxylin-eosin or periodic acid–Schiff. Specimens with suspected epithelial implantation were immunostained using the avidin biotin complex method4 for the anticytokeratin antibodies AE1/AE3 (Dako Corp, Carpentaria, California). Grafts with fibrocellular tissue at the edge of the lenticule were immunostained with smooth-muscle actin (Dako Corp). Seven cases were also examined using transmission electron microscopy. Briefly, a portion of each specimen was fixed in glutaraldehyde, 2.5%, and postfixed in 0.1M cacodylate buffer and osmium tetroxide, 1%. The specimens were dehydrated and embedded in epoxy resin, and 0.1-μm-thick sections were cut and stained with toluidine blue. Ultrathin sections were obtained and were stained with uranyl acetate and lead citrate. Examination was performed using a transmission election microscope (JEOL 100CX II; JOEL Ltd, Tokyo, Japan). After Emory University institutional review board approval was granted, the medical records of the corresponding patients were retrospectively reviewed.