The response of melanopsin-containing retinal ganglion cells (mRGCs) to light exposure is slow and lasts even after termination of light exposure. In this study, we evaluated changes in pupil diameter with flicker light stimuli of different duty ratios. Eight subjects were in dim light for 5 min. Subsequently, they were exposed to light of different duty ratios for 5 min, and their pupil diameters were measured. Light conditions with duty ratios of 70％ and 90％ showed significantly higher tendency to contract pupil diameter than light condition of 100％ duty ratio. In conclusion, the response of mRGCs to higher duty ratio flicker light may not be equal to their response to non-flicker light.
