Human excimer laser lamellar keratectomy. A clinical study.

The first ten blind human eyes in the United States to receive excimer laser (ArFl 193 nm) lamellar keratectomy (reprofiling) are presented. Seven of these patients were followed 6 to 12 months after ablation. All eyes are grossly clear in the region of ablation. Results of slit-lamp examination of all flattened ablated areas show mild superficial haze at the epithelial/stromal interface. This haze might not interfere significantly with vision in patients 7 to 10. Serial pachymetry and keratometry measurements, refraction, and digital keratoscopy show a progressive filling in of the excavated area by approximately two thirds but a loss of initial diopteric correction of only one third. Histopathologic analysis was obtained for four eyes. Transmission electron microscopy of three eyes enucleated 3 to 12 days after ablation shows 40-microns ablation depths through Bowman's layer and superficial stroma with minimal adjacent tissue damage and no inflammatory cells. The epithelium is increased in thickness by 50%, and firmly attached to the underlying stroma. A 4-month postablation specimen shows keratocyte activation with increased protein synthesis (presumed collagen and ground substance).