Multiple-pulse damage thresholds of retinal explants in the ns-time regime.

Scarlett Lipp,Philipp Elmlinger,Wilhelm Stork,Sebastian Kotzur

doi:10.1364/boe.412012

Abstract

The data situation of laser-induced damage measurements after multiple-pulse irradiation in the ns-time regime is limited. Since the laser safety standard is based on damage experiments, it is crucial to determine damage thresholds. For a better understanding of the underlying damage mechanism after repetitive irradiation, we generate damage thresholds for pulse sequences up to N = 20 000 with 1.8 ns-pulses using a square-core fiber and a pulsed Nd:YAG laser. Porcine retinal pigment epithelial layers were used as tissue samples, irradiated with six pulse sequences and evaluated for damage by fluorescence microscopy. The damage thresholds decreased from 31.16 µJ for N = 1 to 11.56 µJ for N = 20 000. The reduction indicates photo-chemical damage mechanisms after reaching a critical energy dose.

Highlights

Lasers are classified for safety reasons based on their potential to cause injury to the human eye and skin
For the determination of the accessible emission limits (AELs) for multiple irradiation of pulsed exposures, a correction factor was introduced in the laser safety standard IEC 60825-1, which was empirically derived from damage experiments on non-human primates (NHPs) and on explants [2]
The slope defines the ratio between ED84 to ED50 and is generally used as a quality feature, a step function is ideal for describing the transition from "no damage" to "damage" in dependence of pulse energy [2]

Summary

Introduction

Lasers are classified for safety reasons based on their potential to cause injury to the human eye and skin For this purpose, the accessible emission limits (AELs) per laser safety class are defined for different pulse durations, wavelengths and specified by application-related correction factors [1]. In the thermal damage regime (sub-microsecond range until a few seconds), a pulse additivity could be observed [3] and showed a good agreement with the empiric derived correction factor for multiple-pulses. This kind of damage mechanism could be explained and modeled using the Arrhenius integral based on the thermo-kinetic relationship [4,5]. The aim of this work is to generate data of high pulse numbers that can later be used to describe the trend of damage thresholds and deduce reduction trends based on the underlying cell death mechanism

Objectives

Methods

Results

Discussion

Conclusion