Effects of blue pulsed light on human physiological functions and subjective evaluation

Abstract

BackgroundIt has been assumed that light with a higher irradiance of pulsed blue light has a much greater influence than that of light with a lower irradiance of steady blue light, although they have the same multiplication value of irradiance and duration. We examined the non-visual physiological effects of blue pulsed light, and determined whether it is sensed visually as being blue.FindingsSeven young male volunteers participated in the study. We placed a circular screen (diameter 500 mm) in front of the participants and irradiated it using blue and/or white light-emitting diodes (LEDs), and we used halogen lamps as a standard illuminant. We applied three steady light conditions of white LED (F0), blue LED + white LED (F10), and blue LED (F100), and a blue pulsed light condition of a 100-μs pulse width with a 10% duty ratio (P10). The irradiance of all four conditions at the participant's eye level was almost the same, at around 12 μW/cm2. We measured their pupil diameter, recorded electroencephalogram readings and Kwansei Gakuin Sleepiness Scale score, and collected subjective evaluations. The subjective bluish score under the F100 condition was significantly higher than those under other conditions. Even under the P10 condition with a 10% duty ratio of blue pulsed light and the F10 condition, the participant did not perceive the light as bluish. Pupillary light response under the P10 pulsed light condition was significantly greater than under the F10 condition, even though the two conditions had equal blue light components.ConclusionsThe pupil constricted under the blue pulsed light condition, indicating a non-visual effect of the lighting, even though the participants did not perceive the light as bluish.

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“…The performance of blue light is probably supported by the non-image-forming effects related to the intrinsically photosensitive retinal ganglion cells (ipRGCs), which have been demonstrated in previous studies to increase the brain arousal level (Lockley et al, 2006;Lee et al, 2008;Katsuura et al, 2012). The recent discovery of 'non-visual' retinal receptors has confirmed an anatomical basis for the observed biological effects of light, with the photopigment melanopsin playing an essential role in phototransduction (Berson et al, 2002).…”

Physiological Effects of Blue Pulsed LED in an Indoor Lighting Environment

“…either by a steady exposure, short interrupted periods of exposure, or at a continuous pulsed rate [21] [22] [23] .…”

“…There are studies that reports physiological changes upon addition of pulsed light at frequencies not visible to the human eye, either by single pulses or by a train of continuous pulses during spaced lapses of time, but all of them during absence of any other lighting in the ambiance, implying the improvement on alertness levels [21] [24] .…”

“…The use of a dimmed LED light superimposed to a task lamp was decided to comply with the references that even with small amounts of blue light, physiological changes can be perceived [21] [24] . Also, dimming light may reduce the subjective perception of working in a blueish ambiance which may affect qualitative perception; and finally, dimming a LED light will not affect the irradiance emitted and will reduce power consumption turning into an economical benefit for the facilities who may use it.…”

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“…Receiving pulsated light over long periods of time can cause users long term problems to mood and to the pupils of their eyes [106]. …”