We know that when human eyes receive visible light, they generate visual signals through cone cells and rod cells of the retina, which are transmitted to the brain, and generate visual images of the objective world, achieving observation and understanding of the surroundings.
But a phenomenon that cannot be ignored is that some blind people with congenital disorders have lost their function of vertebrae and rod cells, but their pupils can still respond to light and maintain normal biological rhythms. Some blind people with removed eyeballs suffer from symptoms such as circadian rhythm disorders and sleep disorders. It is speculated that in addition to vertebrae and rod cells, there are other photoreceptors on the retina.
In 2002, David Buson and others from Brown University in the United States confirmed through experimental research that the third type of photoreceptor cells exist on the mammalian retina - intrinsic photosensitive retinal ganglion cells (ipRGCs). Cone and rod cells are responsible for vision, while the third type of photoreceptor cells (ipRGCs) control the physiological rhythm of a person. The discovery of
's third type of photoreceptor cells (ipRGCs) has promoted the research and confirmation of non-visual light effects and opened up the "sunlight road" for light health.
On the one hand, the third type of photoreceptor cells (ipRGCs) are involved in regulating many non-visual biological effects in the human body, including changes in human life characteristics, hormone secretion and excitation. On the other hand, the 2017 Nobel Prize in Physiology or Medicine awarded three sciences: , Jeffrey Hall, , , Michael Rosbash, and Michael Young. Colin Pitrig, the founder of time biology, proposed that "the biological clock can be pulled by periodic environmental signals." Between many factors such as light, eating time, ambient temperature, social activities, and drug regulation, light is the most powerful timing factor in the synchronization of the biological clock.
passes through the non-visual channel of light, and the light signal passes through the intrinsic light-sensitive retinal ganglion cells (ipRGC) on the retina. The result of signal transmission is that it affects hormone secretion through pineal gland , which ultimately affects the human circadian rhythm. Various human phenotypic indicators including alertness, cortisol , melatonin, core temperature, sleep, etc., which are consistent with the human rhythm, are also affected by this channel. At the same time, ipRGC is also an important mechanism for pupil contraction.
The non-visual biological effects of human eyes show that light and lighting are closely related to human health, mental state, comfort, alertness, attention, work efficiency, etc. With in-depth research in lighting science, medicine and biology, it has been revealed that light can regulate the biological rhythm of the human body by stimulating melatonin secretion, so that people can interfere with people's negative emotions and improve certain diseases by controlling lighting parameters and lighting environment.
In short, the rhythm effect and emotional effect of light are formed through non-visual light stimulation. The rhythm effect of light helps people regulate circadian rhythm and improve sleep disorder , and the emotional effect of light helps people improve mood disorders and cognitive impairment .
