Systematic infrared ablations with the mark IIIFEL at 2.94 mu m in the chicken cornea

Introduction. Previous studies with the free electron laser have only asses sed the corneal tissue response in ex vivo models. This is the first free e lectron laser investigation that has examined the clinical and histologic r esponse of the cornea in vivo. Methods. The Mark III free electron laser wa s tuned to 2.94 mu m for a total of 212 separate in vivo 1 mm spot ablation s at varied fluences (0.4-2.04 J/cm(2)), repetition rates (1-15 Hz), and nu mber of pulses (1-32). Also, 22 separate in vivo central scanning patterns were performed. Results. For the in vivo chicken cornea, the threshold of a blation is approximately 0.64 J/cm(2) at a repetition rate of 10 Hz. Clinic al biomicroscopy and light microscopy revealed parameter-dependent collater al damage (10-40 mu m) induced by laser energy. Wound healing following fre e electron laser ablation exhibits patterns similar to those seen in excime r laser anterior keratectomy, including increased epithelial thickness, new collagen deposition, increased numbers of keratocytes, and patterns congru ent with attempted profiles of myopic ablation. Conclusions. With further s tudy, continued parameter adjustment, and refined delivery schemes, the pot ential for marked improvement and possible application appears promising. ( C) 1999 Elsevier Science B.V. All rights reserved.