Systematic infrared ablations with the mark III FEL at 2.94 μm in the chicken cornea

Abstract

Introduction. Previous studies with the free electron laser have only assessed the corneal tissue response in ex vivo models. This is the first free electron laser investigation that has examined the clinical and histologic response of the cornea in vivo. Methods. The Mark III free electron laser was tuned to 2.94 μm for a total of 212 separate in vivo 1 mm spot ablations at varied fluences (0.4–2.04 J/cm 2), repetition rates (1–15 Hz), and number of pulses (1–32). Also, 22 separate in vivo central scanning patterns were performed. Results. For the in vivo chicken cornea, the threshold of ablation is approximately 0.64 J/cm 2 at a repetition rate of 10 Hz. Clinical biomicroscopy and light microscopy revealed parameter-dependent collateral damage (10–40) μm) induced by laser energy. Wound healing following free electron laser ablation exhibits patterns similar to those seen in excimer laser anterior keratectomy, including increased epithelial thickness, new collagen deposition, increased numbers of keratocytes, and patterns congruent with attempted profiles of myopic ablation. Conclusions. With further study, continued parameter adjustment, and refined delivery schemes, the potential for marked improvement and possible application appears promising.