Evaluation of the potential eye hazard at visible wavelengths of the supercontinuum generated by an ultrafast NIR laser in water

Abstract

Lasers with ultrashort pulse durations have become ubiquitous in various applications, including ocular surgery. Therefore, we need to consider the role of nonlinear optical effects, such as supercontinuum generation during propagation within the ocular media, when evaluating their potential hazard. We used a NIR femtosecond laser to generate a supercontinuum within an artificial eye. We recorded the visible spectra of the supercontinuum generated and calculated the energy contained within the visible band. Our results indicate that for wavelengths between 1350 nm and 1450 nm the energy contained within the visible band of the generated white light supercontinuum may surpass current safety exposure limits, and pose a risk of injury to the retina.

Evaluating the retinal hazard from exposures to the supercontinuum generated by a NIR femtosecond laser

“…The first question guided the choice of wavelengths. At 1200 nm the threshold energy for SC generation in water is much higher than the energy corresponding to the MPE limit based on a previous published study with a waterfilled artificial eye that mimicked a non-human primate's eye 19 . Consequently, exposures at 1200 nm are a negative control because there was no expectation of generating a SC within the eye.…”

“…Consequently, exposures at 1200 nm are a negative control because there was no expectation of generating a SC within the eye. In contrast, at 1350 nm the threshold energy for SC generation in water is slightly lower than the energy corresponding to the MPE limit, barring any differences in the optics and experimental conditions between the previous study 19 and the current one, allowing us to directly address the second question.…”

“…These observations led to the notion that when ultrashort NIR pulses enter the eye, there is the potential for generating SC in the aqueous tissues (such as the vitreous humor), where the VIS pulses generated can potentially damage the retina. Two recent experimental studies demonstrated SC generation within an excised porcine eye 18 water-filled artificial eye designed to emulate the path length and focusing geometry of a non-human primate's eye 19 . Therefore, nonlinear optical interactions between femtosecond NIR pulses and the tissues of the eye need to be considered when evaluating the potential hazard of ultrashort NIR lasers to the retina 20,21 .…”