Purchase this article with an account.
Garen V. Vartanian, Xiwu Zhao, Kwoon Y. Wong; Using Flickering Light to Enhance Nonimage-Forming Visual Stimulation in Humans. Invest. Ophthalmol. Vis. Sci. 2015;56(8):4680-4688. doi: 10.1167/iovs.15-16468.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Intrinsically photosensitive retinal ganglion cells (ipRGCs) mediate nonimage-forming visual functions such as pupillary constriction and circadian photoentrainment. Optimizing daytime nonimage-forming photostimulation has health benefits. We aimed to enhance ipRGC excitation using flickering instead of steady light.
Human subjects were tested with a three-dimensional matrix of flickering 463-nm stimuli: three photon counts (13.7, 14.7 and 15.7 log photons cm−2), three duty cycles (12%, 47%, and 93%) and seven flicker frequencies (0.1, 0.25, 0.5, 1, 2, 4, and 7 Hz). Steady-state pupil constrictions were measured.
Among stimuli containing 13.7 log photons cm−2, the one flickering at 2 Hz with a 12% duty cycle evoked the greatest pupil constriction of 48% ± 4%, 71% greater than that evoked by an equal-intensity (12.3 log photons cm−2 s−1) continuous light. This frequency and duty cycle were also best for 14.7 log photons cm−2 stimuli, inducing a 58% ± 4% constriction which was 38% more than that caused by an equal-intensity (13.3 log photons cm−2 s−1) constant light. For 15.7 log photons cm−2 stimuli, the 1-Hz, 47% duty cycle flicker was optimal although it evoked the same constriction as the best 14.7 log photons cm−2 flicker.
Pupillary constriction depends on flicker frequency and duty cycle besides intensity. Among the stimuli tested, the one with the lowest photon count inducing a maximal response is 13.3 log photons cm−2 s−1 flickering at 2 Hz with 12% duty cycle. Our data could guide the design of healthier architectural lighting and better phototherapy devices for treating seasonal affective disorder and jet lag.
This PDF is available to Subscribers Only