Nanosecond multipulse retinal damage thresholds of elongated irradiance profiles in explant measurements and simulations

Abstract

Significance: The database for multipulse retinal damage thresholds for the laser safety standard (IEC 60825-1:2014) is confined, especially for elongated irradiation profiles. To ensure eye safety, retinal damage thresholds (${\mathrm{ED}}_{50}$ values) need to be determined.

Aim: This study aims to examine nanosecond multipulse scenarios.

Approach: To determine ${\mathrm{ED}}_{50}$ values in ex vivo measurements, an optical laser setup is presented. Porcine explant tissue is irradiated with rectangular top-hat profiles. Thermal simulations are carried out on a validated computer model and retinal injury thresholds are obtained.

Results: The measurements resulted in ${\mathrm{ED}}_{50}$ values from 8.46 to $42.72\mu J$ with a slope from 1.15 to 1.4. A thermal damage in the measurements can be excluded due to the level value in combination with a different type of declining behavior for increasing pulses compared to the simulations. A dependence with increasing elongation or area of the retinal image emerges in the simulations but could not be confirmed in the measurements due to the influencing factors (biological variability, focusing, and measuring procedure).

Conclusions: Using slit apertures for beam shaping, variable rectangular spot geometries are realized without changing elements in the setup. For further evaluation of the behavior of elongated irradiation profiles, additional measurements to improve the measurement accuracy are necessary.

Keywords: IEC 60825-1; laser and eye safety; laser induced retinal damage; laser tissue interaction; multipulse retinal damage experiments; thermal simulation.