Axial length reduction and choroidal thickening with short‐term exposure to cyan light in human subjects

Purpose Given the potential role of light and its wavelength on ocular growth, this study investigated the effect of short‐term exposure to red, cyan and blue light on ocular biometry in humans. Methods Forty‐four young adults and 20 children, comprising emmetropes and myopes, underwent 2‐h sessions of cyan (507 nm), red (638 nm) and broadband white light on three separate days via light‐emitting glasses. Additionally, young adults were exposed to blue light (454 nm) on an additional day. Axial length (AL) and choroidal thickness (CT) were measured in the right eye before the light exposure (0 min), after 60 and 120 min of exposure and 30 min after light offset using an optical biometer and optical coherence tomographer, respectively. Results Compared to broadband light, exposure to red light resulted in a significant increase in AL (mean difference between white and red light at 120 min, +0.007 mm [0.002]), but no significant change in CT, while cyan light caused a significant AL reduction (−0.010 mm [0.003]) and choroidal thickening (+0.008 mm [0.002]) in young adults (p