Research On Non-Visual Photosensitive System Based On Pupil Contraction

Light, which creates images through human eyes, can affect circadiain rhythm and health of human bodies in physiological, psychological, and biological ways. The detection of intrinsically photosensitive retinal ganglion cells (ipRGCs) provides neurological grounds for the non-visual effects of light. These cells regulate circadian clock, and take part in pupillary light reflex through non-visual neural pathways, which can affect mood, sleep quality, alertness even healthiness. Now we know illumination has both visual and biological effects, but those two effects require different lighting flux, spectrum, light distribution and timing of light. Therefore, it is urgent to build a new set of lighting norms and frames based on human healthy needs.This paper summarises the current studies about non-visual photosensitive system, and introduces the neural pathways of both visual and non-visual systems of human eyes. The characteristics of the third photosensitive cells are analysesd, including their influences on melatonin suppression and pupillary light reflex. On the foundation of that, this study chooses the pupil contraction as the key parameter of non-visual system, and focuses on the spectrum response characteristics of pupil contraction, circadian rhythm and features on different retina regions.A set of experiment equipment was built to analnyse the dynamic contraction of the pupils, based on digital infra-red image processing. In MATLAB environment, a image processing software has been developed to capture the diameter of the pupil in each frame of image, then the pupil contraction response curves under different light stimulation was achieved.48 persons have taken part in the experiments, which produced 1062 minutes long of video files with the size around 70GB.Through statistics of the experimental data, the contribution and influence of three retinal photosensitive cells on pupil constraction responses under different visual environments is studied. Pupil contraction spectrum response curve under photopic vision is achieved through regression analysis and mathematical modeling. This paper considers pupil contraction is real-time and repeatable, and the three photosensitive cells take part in different response stages of pupil contraction. Therefore, through studying pupil constraction, we can acquire more understanding of the mechanism of how three photosensitive cells work on each other during non-visual process. And a math model can even be built through large quantity of sampling and data.In this paper, the effects of circadian rhythm and light on different regions of the retina on pupil contraction are also discussed, in order to broaden this study of non-visual photosensitive system.Besides experiments, the paper also adapts theoretical research and lighting practices. The relationship between indoor lighting environment and feeling/well-being of human is analyzed, by the means of on-site lighting measurement and questionnaires.This study helps to understand the intrinsically photosensitive retinal ganglion cells (ipRGCs), and construct a new system of indoor lighting norms and evaluations, based on human healthy needs.