Human excimer laser keratectomy. Clinical and histopathologic correlations.

Abstract

To understand the healing capabilities of the diseased human cornea after excimer laser photoablation by morphologic analysis of laser-treated corneas. Twelve corneal specimens were obtained 5 to 16 months after lamellar or full-thickness keratoplasty following phototherapeutic keratectomy for undercorrected myopic epikeratoplasty (2 eyes), corneal leukomas (2 eyes), herpes zoster corneal scarring (1 eye), band keratopathy (2 eyes), adenoviral subepithelial opacity (1 eye), keratoconus (1 eye), herpes simplex corneal scarring (2 eyes), granular corneal dystrophy (1 eye), and recurrent lattice dystrophy (1 eye). The morphology of the corneas was examined by light and electron microscopy. Epithelial hyperplasia, abnormal epithelial attachment, and disorganized stromal matrices were observed. Evidence of residual disease frequently observed in these specimens indicated that the pathology either was not excised at the time of laser keratectomy or was recurrent. The response of the diseased cornea to excimer laser treatment has similar characteristics to the responses previously observed in animal studies. Incomplete ablation of diseased tissue and/or recurrence of the initial disease was the major reason for failure of the treatment. Possible causes for the inability to remove diseased tissues and superficial scars with the excimer laser include (1) insufficiently achieved ablation depth and/or diameter and (2) decreased laser ablation rates of scarred cornea.