The voltage of a power supply could be regulated by two adjustable resistors for each of the two high power LEDs (a RGB LED and a phosphor converted LED) at a color temperature of 6500 K.įigure 1. Ltd) was used to diffuse light rays equally. An integrating sphere of 50 cm diameter (Everfine Instrument Co. The set-up of equipment was schematically illustrated in Figure 1. All participants took part under the ethical guidelines of Changzhou Institute of Technology. None of the participants had eye problems or general health complaints. The aims and procedures of the experiment were told to them and informed consent was given by them before testing. Twenty university students, ranging in age from18 to 23 years (mean =21) voluntarily participated in this study. In this study, the pupil diameters at different time of a day were measured to deduce the relationship between cirtopic effect on pupil size and time of a day. Whether the cirtopic effect on pupil size depends on time of a day has not been examined yet. However, all past investigations of cirtopic effect on pupil size were conducted at a certain time of the day by researchers. It is evidenced that the pupil size, an important factor of visual performance, is influenced by this cirtopic effect. The discovery of a new class of photosensitive cells in the retina, the intrinsically photosensitive retinal ganglion cells (ipRGCs), which send retinal information induced by ambient light to the brain center to partly control the physiological characteristics of human, the pupil size, leads researchers to explore how the ipRGCs react under different luminance conditions.
Pupil size, ipRGC, pupil light reflex, cirtopic IntroductionĪ number of studies have been conducted to develop the mechanism and equations between pupil size and luminance. Therefore, cirtopic effect on pupil size was time of day dependent Key words It was found that the cirtopic effect on pupil size was not statistically different in day time, but significantly different in night time, especially in midnight. Twenty healthy volunteers were tested at 09:00,15:00, 21:00 and 02:00 for-five working days. The cirtopic effect induced by these two light sources was characterized by steady-state pupil diameter. Two kinds of lights, a phosphor converted LED and a RGB LED, with the same photopic luminance and color temperature but different cirtopic luminance were chosen as the experimental light sources. The present study investigated the time of day effect on steady-state pupil size induced by cirtopic effect.