Why do some epikeratoplasties fail?

We performed a morphologic analysis of nine epikeratoplasty lenticules that were removed due to nonhealing epithelial defects, interface opacity, and/or haze of the donor lenticule. Structural abnormalities were found in all layers of the donor lenticules, with the major changes being present in the surface epithelium and Bowman's layer. Significant changes in the stromal collagen were documented. Similar changes were found in a previous analysis of never-used, factory-prepared lenticules that had been prepared following the use of a corneal press and a lyophilization process. This study suggests that the presently used process of tissue preparation may be deleterious to the structure of the donor lenticule and may adversely affect surface reepithelialization. The placement of the lenticule above the recipient's Bowman layer may be an additional retardant to postoperative reepithelialization.