Violet Light Is Abundant Outdoors but Deficient Indoors in Modern Lifestyle in Tokyo

This study examines the role of violet light (VL) in preventing myopia progression, addressing a critical need in urban environments where VL exposure is limited. Recent research suggests that VL, within the 360-400 nm wavelength range, may reduce myopia risk. To investigate, we conducted spectroscopic measurements in various settings across Tokyo, quantifying VL irradiance in natural sunlight. The results showed high VL levels outdoors, averaging 583 μW/cm² on sunny days and 271 μW/cm² on cloudy days, leading to a weighted annual average of approximately 310 μW/cm². In contrast, indoor environments lacked VL due to UV-blocking materials in windows, glasses, and lighting. This deficiency may contribute to the rising incidence of myopia, particularly in urban areas with reduced outdoor exposure. Our findings highlight the need for innovative solutions to mitigate VL deficiency indoors, such as optimizing architectural designs and artificial lighting to better incorporate VL. This study provides foundational insights for future interventions aimed at reducing myopia risk through improved indoor light environments.