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Photic Input Thresholds

Meaning

Photic Input Thresholds define the minimum and maximum levels of light intensity, measured in lux, and the specific light spectrum necessary to elicit a desired physiological response from the body’s non-visual photoreceptors. The most clinically significant threshold is the intensity required to effectively suppress nocturnal melatonin secretion and signal wakefulness to the master circadian clock, which is particularly sensitive to blue-light wavelengths. Understanding these individual thresholds is vital for designing effective light hygiene protocols that either maximize circadian entrainment in the morning or ensure complete darkness and hormonal rest at night. These thresholds can exhibit individual variability based on factors like age and retinal health.