Photoreception for Circadian, Neuroendocrine, and Neurobehavioral Regulation

Abstract

In the art and science of lighting, four traditional objectives have been to provide light that: 1) is optimum for visual performance; 2) is visually comfortable; 3) permits aesthetic appreciation of the space; and 4) conserves energy. Over the past 25 years, it has been demonstrated that there are nonvisual, systemic effects of light in healthy humans. Furthermore, light has been used to successfully treat patients with selected affective and sleep disorders as well as healthy individuals who have circadian disruption due to shift work, transcontinental jet travel, or space flight. Recently, there has been an upheaval in the understanding of photoreceptive input to the circadian system of humans and other mammals. Analytical action spectra in rodents, primates, and humans have identified 446-484 nm (predominantly the blue part of the spectrum) as the most potent wavelength region for neuroendocrine, circadian, and neurobehavioral responses. Those studies suggested that a novel photosensory system, distinct from the visual rods and cones, is primarily responsible for this regulation. Studies have now shown that this new photosensory system is based on a small population of widely dispersed retinal ganglion cells that are intrinsically responsive to light, and project to the suprachiasmatic nuclei and other nonvisual centers in the brain. These light-sensitive retinal ganglion cells contain melanopsin, a vitamin A photopigment that mediates the cellular phototransduction cascade. Although light detection for circadian and neuroendocrine phototransduction seems to be mediated principally by a novel photosensory system in the eye, the classic rod and cone photoreceptors appear to play a role as well. These findings are important in understanding how humans adapt to lighting conditions in modern society and will provide the basis for major changes in future architectural lighting strategies.

Factors That Influence Standard Automated Perimetry Test Results in Glaucoma: Test Reliability, Technician Experience, Time of Day, and Season

“…Adjustments to the circadian pacemaker are made by exposure to environmental light through intrinsically photosensitive retinal ganglion cells containing melanopsin. 27,28 Effects of time of day are difficult to interpret because they are influenced by interindividual differences in circadian period length, circadian phase, sleep duration, and the duration of prior wakefulness, vulnerability to sleep loss, age, and personality. 6 Several researchers examined circadian rhythms in visual thresholds.…”

Neurobehavioral, health, and safety consequences associated with shift work in safety-sensitive professions

“…The color of the light is also important; most recently it has been reported that light in the blue part of the spectrum (446-484 nm) is the most potent region of the wavelength for circadian responses [57]. Melatonin can be used to facilitate a shift in the circadian system to align with night shift work [58].…”

Ocular hazards of blue-light therapy in dermatology

“…20 These blue-lightsensitive photoreceptors send vital information to nonvisual brain centers that mediate circadian rhythms, neuroendocrine and neurobehavioral responses, metabolic homeostasis, stress response, and production of serotonin and melatonin. [21][22][23][24][25] Irreversible damage to photoreceptive cells may disrupt these biological systems, resulting in associated problems including insomnia, memory loss, and depression. 26 Moreover, several studies have shown that the retinal pigmented epithelium (RPE), a cellular layer attached to the retina and responsible for its nourishment, is damaged or destroyed by excessive blue-light exposure.…”