Nanosecond multiple pulse <i>ex vivo</i> model of laser retinal damage

Pulsed lasers operating in the nanosecond time regime are increasingly used in a variety of applications, but safety data for the wide scope of laser parameters are limited. Specifically, repetition frequency, pulse duration, and wavelength may influence whether multiple successive pulses produce additive, synergistic, or interfering effects. Testing all these parameters in vivo would be costly and time consuming, while in vitro models lack the full complexity of the tissue composition and structure. An ex vivo model represents a happy medium between the two. Thus, the authors present a porcine ex vivo explant system to study nanosecond regime multiple pulse laser eye damage. The authors conducted laser exposures at 532 and 1064 nm, with pulse trains of 1, 10, 100, 1000, 10 000, and 20 000 pulses, and determined probit ED50 values for both wavelengths. Results from the 532 nm exposures were consistent with those from the previously published literature, and the trend was well fit by a probability summation model. Relative to 532 nm, exposures at 1064 nm revealed dramatic differences in lesion morphology and total energy required to induce damage, and the relationship between the total number of pulses and ED50 instead followed a logarithmic decrease. The authors demonstrate that this ex vivo model has the capability to reveal key insights underlying laser retinal damage mechanisms and represents a powerful tool for rapidly and affordably testing a wide variety of exposure conditions and how they influence the susceptibility of the retina to laser damage from multiple pulse exposures in the nanosecond time regime.