Corneal damage effects induced by infrared optical parametric oscillator radiation at 3743 nm

The main aim of this paper is to investigate the corneal damage effects induced by mid-infrared optical parametric oscillator (OPO) radiation. Experiments were performed to determine the corneal damage thresholds of New Zealand white rabbit at the wavelength of 3743 nm for exposure durations of 0.1 s, 1.0 s and 10.0 s. Through slit-lamp biomicroscope and histopathology, corneal injury characteristics were revealed. The damage thresholds were 3.73 J/cm2, 7.91 J/cm2 and 31.1 J/cm2, respectively, for exposure durations of 0.1 s, 1.0 s and 10.0 s. The damage data was correlated by an empirical equation: Radiant exposure at the threshold = 9 . 7 2 × exposure duration, 0 . 4 6 where the units of radiant exposure and exposure duration were J/cm2 and second. At near-threshold level, corneal injuries at 1 h post-exposure mainly involved the epithelium, and the epithelium damages repaired at 24-h post-exposure. There are sufficient safety margins between the damage thresholds and the maximum permitted exposures from current international laser safety standard IEC 60825-1.