Study of the Effects of Multiple-Pulsed Laser Exposure on Increment Thresholds

摘要

Little is known about the effects of brief, repetitive laser pulses in the microsecond and sub-microsecond range on visual adaptation. Although it is generally acknowledged that, for pulsed light exposures from 1 to 150 ms, the total energy of a flash (intensity x duration) determines its brightness or adaptation potential, there are little data supporting this reciprocal relationship in human subjects. The purpose of this study was to compare the increment threshold for a spot target superimposed on an extended source image of a pulsed laser source, and to evaluate whether reciprocity holds. Eight subjects completed a method-of-adjustment determination of increment threshold for a 023 white test spot viewed superimposed on an extended source image (0.61) of a green (532 nm) laser beam. The laser pulse durations were 10 micro s, 100 micro s, 1 ms and 10 ms at 3 Hz and 10Hz. In addition, the effect of continuous wave (CW) exposure was determined. The time-average laser exposure was held constant across all the laser conditions. For the 3 Hz pulse condition, the threshold luminance was much lower than for the CW condition and there was no effect of pulse width, i.e. reciprocity was observed. However, thresholds for the 1 ms and 10 ms pulses at 10 Hz were higher than for the DW case, and this reciprocity failure was interrupted as a brightness enhancement effect More pulse durations and pulse rates must be studied before this failure can be more fully understood.