Purpose: To understand the healing capabilities of the diseased human
cornea after excimer laser photoablation by morphologic analysis of la
ser-treated corneas. Methods: 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 tester 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 electro
n microscopy. Results: Epithelial hyperplasia, abnormal epithelial att
achment, 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. Conclusions: 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 rem
ove diseased tissues and superficial scars with the excimer laser incl
ude (1) insufficiently achieved ablation depth and/or diameter and (2)
decreased laser ablation rates of scarred cornea.