Epithelial ingrowth after laser in situ keratomileusis: a histopathologic study in human corneas.

OBJECTIVE To report the histopathologic findings in 4 human corneas that developed epithelial ingrowth after laser in situ keratomileusis (LASIK), at various postoperative intervals. METHODS One specimen was obtained intraoperatively during treatment of epithelial ingrowth 2 months after LASIK (case 1). The other 3 corneal specimens were obtained after penetrating keratoplasty performed at 7 months (case 2), 20 months (case 3), and 5 years (CASE 4) after LASIK. The specimens were examined with both light and transmission electron microscopy. RESULTS In case 1, most of the epithelial cells under the flap looked viable. However, some had begun to lose their characteristic shape and intercellular contacts. In case 2, aggregations of nonactivated fibroblasts and degrading epithelial cells could be observed. The surrounding collagen matrix differed significantly from that of the intact corneal matrix. In case 3, only completely degraded epithelial cells could be found, surrounded by collagen fibrils approximately 2 to 2.5 times larger in diameter than typical corneal collagen. In case 4, epithelial cell remnants, surrounded by a continuous layer resembling the basal membrane, were observed. CONCLUSIONS Corneal epithelial cells lose their characteristic morphologic features and eventually degrade in the metabolically "unusual" environment of the flap interface. Concurrently, a capsule of connective tissue similar to scar tissue forms, separating them from healthy cornea.