Effects of Temporal Light Modulation on Working Performance, Subjective Visual Fatigue and Pupillary Light Response at 50 lx

Abstract

Recent studies revealed that the visual perception of temporal light modulation (TLM), particularly the visibility threshold, were illuminance dependent and subjects exhibited significantly different response at 50 lx. Some novel studies suggested TLM at 50 lx could be particularly useful in terms of promoting alertness and increasing comfort. Therefore, in this study, working performance, subjective visual fatigue and pupillary light response (PLR) were measured under different frequency of TLM at 50 lx to evaluate such phenomenon and its possible application. Results showed that all three parameters measured at 50 lx followed a U-shaped curve with the increasing frequency, instead of the monotonically increasing trend reported in earlier research at relative higher illuminance levels (300–400) lx. Comparing to 100 Hz or 1000 Hz, 300 Hz was the best in terms of visual fatigue (P<0.01) and worst in terms of working performance (P<0.01) while PLR also showed smaller percent change under 316 Hz and 562 Hz (P<0.01). These results supported the hypotheses that at 50 lx illuminance level, the relationship between the effect of TLM and frequency was non-monotonic and was different than the monotonically increasing trend discovered under higher illuminance. Furthermore, such difference not only affects working performance and visual fatigue, but also pupillary light response, which then might affect more physiological outcome. These results could potentially be useful for reducing visual fatigue at scenarios such as operating displays in vehicles or aircrafts at night.