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

Abstract

Background: The simultaneous exposure to blue and green light was reported to result in less melatonin suppression than monochromatic exposure to blue or green light. Here, we conducted an experiment using extremely short blue-and green-pulsed light to examine their visual and nonvisual effects on visual evoked potentials (VEPs), pupillary constriction, electroretinograms (ERGs), and subjective evaluations. Methods: Twelve adult male subjects were exposed to three light conditions: blue-pulsed light (2.5-ms pulse width), green-pulsed light (2.5-ms pulse width), and simultaneous blue-and green-pulsed light with white background light. We measured the subject's pupil diameter three times in each condition. Then, after 10 min of rest, the subject was exposed to the same three light conditions. We measured the averaged ERG and VEP during 210 pulsed-light exposures in each condition. We also determined subjective evaluations using a visual analog scale (VAS) method. Results: The pupillary constriction during the simultaneous exposure to blue-and green-pulsed light was significantly lower than that during the blue-pulsed light exposure despite the double irradiance intensity of the combination. We also found that the b/|a| wave of the ERGs during the simultaneous exposure to blue-and green-pulsed light was lower than that during the blue-pulsed light exposure. We confirmed the subadditive response to pulsed light on pupillary constriction and ERG. However, the P100 of the VEPs during the blue-pulsed light were smaller than those during the simultaneous blue-and green-pulsed light and green-pulsed light, indicating that the P100 amplitude might depend on the luminance of light. Conclusions: Our findings demonstrated the effect of the subadditive response to extremely short pulsed light on pupillary constriction and ERG responses. The effects on ipRGCs by the blue-pulsed light exposure are apparently reduced by the simultaneous irradiation of green light. The blue versus yellow (b/y) bipolar cells in the retina might be responsible for this phenomenon.

Do green-blocking glasses enhance the nonvisual effects of white polychromatic light?

“…Woelders et al [21] have demonstrated that M- and S-cones provide inhibitory input to the pupillary control system, whereas L-cones and melanopsin response present an excitatory role. These findings support a subadditive response to light, where the effects of blue light are reduced by green or polychromatic light exposure, as in the previous studies [6, 7] and the present study.…”

“…However, Figueiro et al [16] found that simultaneous exposure to blue and green light resulted in reduced melatonin suppression, compared with monochromatic light exposure to blue or green light; this was referred to as a subadditive response to light. We also verified that simultaneous blue and green light exposure resulted in less pupillary constriction than blue light exposure [6, 7]. These findings indicated that the effect of blue light was inhibited by simultaneous exposure to green light.…”

“…We used white-pulsed LED light (1000 lx, pulse width 2.5 ms; 16 W24-AW2S, Kashinoki Sogyo Co., LTD.) for measuring pupillary constriction according to our previous studies [5–7] and white-continuous LED light (1000 lx) for electroencephalogram (EEG) measurement with white background light (100 lx), by using an integrating sphere (Takano Co., Nagano, Japan). We used a background light in order to saturate rods responses [19] and avoid the influence of rods on pupillary contraction as much as possible [7]. The illuminance of light was measured at each subject’s eye level by using a spectroradiometer (CL-500A, Konica Minolta Optics Co., Tokyo, Japan).…”

“…Accordingly, night-shift work and use of portable devices at nighttime have increased rapidly, such that humans are exposed to light, regardless of the time of day or night. Light that contains the blue component stimulates intrinsically photosensitive retinal ganglion cells (ipRGCs) and contributes to melatonin suppression [1, 2] and pupillary constriction [3–7]. Critically, blue light exposure in the evening induces sleep disturbances, transient eye discomfort, and headaches [8, 9].…”

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

“…The number of papers addressing this question has increased over the last years. Papers have mainly focused on the effects of monochromatic light on circadian rhythm [53–57] and pupillary constriction [58–63]. A few other papers have studied on HRV [64–66], time sense and respective event-related potentials [67], electroretinogram (ERG) [68], and body temperature regulation [69].…”