Effect of quantity and intensity of pulsed light on human non-visual physiological responses

Abstract

BackgroundExposure to pulsed light results in non-visual physiological responses in humans. The present study aims to investigate whether such non-visual effects are influenced to a greater extent by the intensity of lighting or by the power (quantity) of lighting.Methods>Twelve healthy young male participants (23 ± 0.3 years, 21–24 age range) were recruited for the present study. Participants were exposed to light of varying levels of intensity and quantity whose frequency was held constant across the conditions, which consisted of exposure to blue (different intensity, constant quantity) and white (constant intensity, different quantity) LEDs. Pupillary constriction, electroencephalogram (EEG) alpha band ratio, subjective sleepiness, concentration and perception of blueness were measured.ResultsPupillary constriction and subjective concentration were significantly greater under the high-intensity and short pulse width (HS) condition than under the low-intensity and long pulse width (LL) conditions at three time points during exposure to high-intensity light. However, no significant differences were observed among the results at the three time points during exposure to different quantities of pulsed light.ConclusionsThe results of the present study indicate that non-visual influences of pulsed light on physiological function are mainly determined not by the quantity but by the intensity of the emitted light, with relatively higher levels of intensity producing more significant physiological changes, suggesting potent excitation of intrinsically photosensitive retinal ganglion cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s40101-017-0137-7) contains supplementary material, which is available to authorized users.

Suppression of salivary melatonin secretion under 100-Hz flickering and non-flickering blue light

“…The development of artificial lighting systems has allowed us to have a bright environment at night, bringing comfort and safety. However, light has also been reported to have a range of physiological impacts on humans, such as changes in pupillary constriction [ 1 – 4 ], autonomic nervous function [ 5 – 7 ], brain activity [ 8 ], and cortisol secretion [ 9 ]. Furthermore, bright light at night is known to delay the circadian phase [ 10 – 12 ], resulting in disruption of the circadian rhythm [ 13 ], which, in turn, can lead to poor sleep and various kinds of health risks, such as cardiac disease and depression [ 14 ].…”

Subadditive responses to extremely short blue and green pulsed light on visual evoked potentials, pupillary constriction and electroretinograms

“…Besides, we found that the pupillary response under the extremely short (pulse width 100 μs) but higher irradiance (11.2 μW/cm 2 or 13.4 log photons/cm 2 /s) blue-pulsed light was significantly greater than that under the steady blue light (1.4 μW/cm 2 or 12.5 log photons/cm 2 /s) which had equal blue light components (the products of irradiance and duration) [ 12 ]. We assumed that the pulsed light of strong irradiance might induce significantly greater pupillary response [ 25 ].…”

A review of the studies on nonvisual lighting effects in the field of physiological anthropology

“…[64]2016Blue (10, 5, 2 lx)Green (71 lx)Red (39 lx)(OLED)Time zone of experiment: 08:30–13:00·Heart rate·HRVYuda E, Ogasawara H, Yoshida Y, Hayano J. [65]2017Blue (483 nm, 13 lx)Green (555 nm, 91 lx)White (158 lx)(OLED)Exposure time: 10 min + 5 min PVT under white fluorescent light (illuminance, 300 lx)Psychomotor vigilance test (PVT)Time zone of experiment: 09:30–14:00·Heart rate·HRV·Reaction time, minor lapse (PVT)Dai Q, Uchiyama Y, Lee S, Shimomura Y, Katsuura T. [61]2017Blue (467 nm)Irradiance: 7.5, 15, 30 μW/cm 2 Pulse width: 50, 100, 200 μsWhite (color temperature 2878 K, 14.75 μW/cm 2 ) (LED)Exposure time: 12 min·Pupillary constriction·EEG·Subjective evaluation (concentration, sleepiness, perception of blueness)Yuda E, Ogasawara H, Yoshida Y, Hayano J. [66]2017Blue (485 nm, 8.02 μW/cm 2 )Orange (622 nm, 6.54 μW/cm 2 )(OLED)Exposure time: 30 min during lunch break5 min of PVT under white fluorescent light (color temperature 4010 K, illuminance 450 lx)Psychomotor vigilance test (PVT)·Heart rate·HRV·Reaction time, minor lapse (PVT)Lee S, Muto N, Shimomura Y, Katsuura T. [62]2017Blue (466 nm)Green (527 nm)Irradiance: 20 μW/cm 2 Pulse width: 1 msInter-stimulus interval: 0, 250, 500, 750, 1000 ms·Pupillary constrictionLee S, Uchiyama Y, Shimomura Y, Katsuura T. [63]2017Blue (464 nm)Green (526 nm)Pulse width: 2.5 msPhoton density: 15.2 log photons/cm 2 /sBlue, green, blue + green·Electroretinogram (ERG)·EEG·Visual evoked potential·Pupillary constriction·Subjective evaluations (bluish, greenish)Kozaki T, Hidaka Y, Takakura JY, Kusano Y.…”

“…Pupillary constriction was found to be greater under high irradiance with short pulse width and under middle irradiance with middle pulse width, when compared with low irradiance with long pulse width condition. These findings indicate that higher intensity with shorter pulsed width of blue pulsed light produces a more significant influence on ipRGCs, even when the quantity of blue pulsed light is held constant [61]. The effects of both simultaneous and successive exposure to blue and/or green pulsed light on PLR were investigated using extremely short pulses (1 ms) of blue and green lights with inter-stimulus intervals (ISIs) ranging from 0 to 1000 ms.…”