Characterization of the fluorescence spectra produced by excimer laser irradiation of the cornea.

The epithelium and stroma of bovine and human corneas were exposed to both ablative and subablative levels of 193-nm excimer laser radiation and the spectra of the induced fluorescence recorded. Two broad peaks in the emission spectra were observed, at 310 nm and 460 nm, with a difference in the relative height of these peaks between epithelium and stroma. The lower cut-off for fluorescence (260 nm) was similar for both tissues. Time-resolved measurements showed that fluorescence occurs on the nanosecond time scale, and an estimate gives the quantum yield for photons emitted in the 260-350-nm range as approximately 1 X 10(-5). The significance of these results in the evaluation of the safety of surgery with an argon fluoride excimer laser is discussed.