To explore the association between light at night (LAN) of different intensities and ocular biometric parameters among preschool children, so as to provide a reference for optimizing strategies for myopia prevention and control.

From November 2024 to January 2025, a cross-sectional study was conducted among 369 preschool children from one kindergarten in Quanzhou City, Fujian Province. Questionnaire survey and eye examination were performed, and portable light sensors were used to collect LAN exposure data. Spearman correlation analysis was used to examine the associations between the duration of LAN exposure at different intensities and ocular biometric parameters. Generalized linear model was employed to explore the relationships between LAN duration at various intensities and ocular biometric parameters, while restricted cubic spline was used to investigate potential nonlinear associations.

The spherical equivalent (SE), axial length (AL), and axial length/corneal radius of curvature (AL/CR) for preschool children were 0.38 (-0.13, 0.63) diopters, 22.35 (21.86, 22.88) mm, and 2.86 (2.82, 2.90), respectively. The median daily duration (interquartile ranges) of LAN exposure at intensities of 0, >0-100, >100-300, and >300 lx were 6.09(5.31, 6.74), 1.74(1.13, 2.42), 0.06(0.00, 0.26), 0.00(0.00, 0.00)h/d, respectively. The generalized linear model showed that for every additional hour of LAN at >100-300 lx, the AL/CR increased by 0.26 (95%CI=0.01-0.52); for every additional hour of LAN at >300 lx, AL/CR increased by 0.32 (95%CI=0.05-0.59) (both P < 0.05). No statistically significant associations were observed between SE or AL and LAN exposure at any of the intensity levels (0, >0-100, >100-300, and >300 lx) (all P>0.05). The restricted cubic spline model revealed that, except for the nonlinear relationship between LAN duration and AL at >100-300 lx (P=0.02), all other light intensity levels showed linear correlations between LAN duration and preschool children's SE, AL, and AL/CR (both P>0.05). Time-of-day subgroup analysis revealed that during school days, for every additional hour of LAN at >100-300 lx and over 300 lx, AL/CR increased by 0.18 (95%CI=0.01-0.35) and 0.22 (95%CI=0.03-0.41), respectively (both P < 0.05). However, weekend exposure showed no statistically significant association (all P>0.05).

Higher intensity of LAN is associated with increased AL/CR, and reducing exposure to LAN may have a potential protective effect on the visual health of preschool children.