Laser-induced retinal damage threshold for repetitive-pulse exposure to 100-μs pulses

Abstract

The laser-induced retinal injury thresholds for repetitive-pulse exposures to 100-μs-duration pulses at a wavelength of 532 nm have been determined for exposures of up to 1000 pulses in an in vivo model. The ED50 was measured for pulse repetition frequencies of 50 and 1000 Hz. Exposures to collimated beams producing a minimal retinal beam spot and to divergent beams producing a 100-μm-diameter retinal beam spot were considered. The ED50 for a 100-μs exposure was measured to be 12.8 μJ total intraocular energy for a minimal retinal beam spot exposure and 18.1 μJ total intraocular energy for a 100-μm-diameter retinal beam spot. The threshold for exposures to N > 1 pulse was found to be the same for both pulse repetition frequencies. The variation of the ED50 with the number of pulses is described well by the probability summation model, in which each pulse is considered an independent event. This is consistent with a threshold-level damage mechanism of microcavitation for single-pulse 100-μs-duration exposures. The data support the maximum permissible exposure levels for repetitive-pulse exposure promulgated in the most recent laser safety guidelines.

A narrow-band speckle-free light source via random Raman lasing

“…Melanin-containing organelles known as melanosomes are the main absorbing particles found in the monolayer of cells of the retinal pigment epithelium (RPE) layer of the retina [25,26]. The formation of small bubbles (microcavitation) is the primary retinal damage mechanism for laser pulses in the 10 −9 to 10 −6 seconds range around the melanosomes in the RPE cells [27,28]. The formation of cavitation bubbles are highly correlated to cell death, and it is critical to understand the relationship between laser irradiance and damage.…”

Wave optical simulation of retinal images in laser safety evaluations

“…It was found that also for the human eye a diffraction limited focus can be achieved [29, 30]. In another study which was done by Lund et al in 2008 [31] measurements on non‐human primates were performed by using wavefront‐corrected beams to reduce refractive errors and aberrations. Though the results show lower thresholds than without using wavefront correction the retinal spot size could not be determined.…”

Thermal damage thresholds for multiple-pulse porcine skin laser exposures at 1070 nm

“…In studies of multiple-pulse exposures in the eye, it is common to present the energy threshold per pulse as a function of the number of pulses in the train. 23,[30][31][32] This approach is useful for visualizing the cumulative effect of pulses but assumes pulses of equal length and pulse trains with a consistent PRF. These parameters are more diverse in our study given that we held TOT constant and varied the pulse duration and PRF to fit the specified duty cycle and number of pulses.…”

“…There has been extensive research into multiple-pulse MVL thresholds in the eye using number of pulses and pulse repetition frequency (PRF) as variables, for the infrared [23][24][25][26] and visible [27][28][29][30][31] wavelength regions. Clark et al 32 provided a theoretical analysis of multiple-pulse thermal damage thresholds to the retina based on the Arrhenius integral model, for both visible and NIR wavelengths.…”