Short-term exposure to cyan light attenuates myopigenic effects of hyperopic defocus on ocular biometry in humans

This study investigated whether short-term exposure to cyan light can inhibit axial elongation and choroidal thinning induced by myopigenic hyperopic defocus in humans. Thirteen myopes (-3.73 ± 1.21 D) and fifteen emmetropes (-0.05 ± 0.11 D), aged of 24.07 ± 3.54 years, were exposed to cyan light (507 nm; total irradiance 3.06 W/m²) and broadband light (3.05 W/m²) using light-emitting glasses for two hours on separate days. Hyperopic defocus (-3D) was imposed on right eye using contact lenses (CL), while the fellow eye experienced no defocus. Ocular biometry, including axial length (AL) and subfoveal choroidal thickness (SFCT), was measured at baseline, after 60 and 120 min of light exposure, and 30 min post light offset. Three-way repeated measures ANOVA revealed that the effects of broadband and cyan light on AL (defocus × time × wavelength interaction, F _(3,162) = 0.37, p = 0.777) and SFCT (F _(3,162) = 0.35, p = 0.787) across all time points did not differ significantly between defocused and non-defocused eyes. However, exposure to cyan light significantly reduced axial elongation (mean difference in AL between cyan and broadband light: -0.011 ± 0.002 mm; Holm-Sidak post hoc test, p = 0.001) and increased SFCT (mean difference: +0.009 ± 0.002 mm; p < 0.001) at 120 min, compared with eyes exposed to the same degree of hyperopic defocus under broadband light. In non-defocused eyes, cyan light resulted in a significant increase in SFCT compared to broadband light at 120 min (mean difference, + 0.010 ± 0.001 mm, p < 0.001), while no significant difference was observed in AL. No significant effect of refractive error was observed in either eye (p > 0.05). Short-term exposure to cyan light can inhibit AL elongation and choroidal thinning induced by hyperopic defocus, warranting further investigations into its long-term potential for myopia control.