LASER-INDUCED FLUORESCENCE DURING PHOTOREFRACTIVE KERATECTOMY - A METHOD FOR CONTROLLING EPITHELIAL REMOVAL

PURPOSE: Laser-induced fluorescence is generated during ablation of co rneal tissue with the argon-fluoride 193-nm excimer laser. To investig ate possible changes in laser-induced fluorescence spectra emitted dur ing the transition between epithelium and stroma, we developed a syste m using an intensified charge-coupled device to achieve fast per-pulse temporal resolution of laser-induced fluorescence. METHODS: Freshly e nucleated human cadaver eyes were subjected to 193-nm excimer laser ke ratectomy. During the procedure, laser-induced fluorescence was measur ed using an intensified charge-coupled device. Changes in laser-induce d fluorescence were detected and used to control epithelial removal. D epth of ablation was determined histologically. RESULTS: The 193-nm ex cimer laser pulses induced both visible and ultraviolet fluorescence f rom corneal epithelium and stroma. In each layer two peaks predominate d, one at 405 nm and the other at 346 nm. There was a rapid threefold reduction in the 346-nm ultraviolet peak at the transition from epithe lium to stroma. CONCLUSION: By monitoring changes in laser-induced flu orescence at the epithelial-stromal interface, the clinician may be ab le to control corneal epithelial removal more precisely and reproducib ly before performing photorefractive ablation.