Characteristics of axial length and interocular axial length difference in Chinese children and teenagers

Abstract Purpose To investigate axial length and interocular axial length difference distributions and correlating factors in Chinese children and teenagers. Methods This study retrospectively reviewed the axial lengths (AL) and interocular axial length differences (ALD) of 4422 children. Sex, ocular alignment, outdoor activities, total media exposure (TV watching and electronic devices), sleep duration, parental myopic state, and parental age and their relationships with mean AL and the ratio of axial length to corneal radius curvature (AL/CR) were assessed. Factors associated with the mean AL, AL/CR, ALD, and the interocular difference in AL/CR (△AL/CR) in all participants and four age groups. Results The mean AL and ALD varied mainly by age. Children with esotropia (in preschoolers, P  = 0.014, 0.029), 15–21 h of outdoor durations per week(all, P  = 0.017), and > 14h total media exposure per week (all, P =  0.033) were more likely to have shorter AL or AL/CR. Esotropia(in primary school, P  = 0.001), shorter weekdays sleep duration (all, P  = 0.009), or long weekend sleep duration (all, P  = 0.033) were positively associated with ALD or △AL/CR. Conclusion AL and ALD were mainly associated with age and esotropia. Sleep duration on weekdays or weekends might associate with the mean or interocular difference in axial length distribution.