Digital Eye Behaviour Phenotypes and Their Association with Axial Length and High Myopia in Chinese Adolescents

PURPOSE: Screen exposure is often summarised as total duration, although this aggregate measure obscures important differences in how devices are used. This study sought to identify digital eye behaviour phenotypes and evaluate their associations with axial length (AL) and high myopia. METHODS: A school-based cross-sectional study of 898 high school students in Shanghai was conducted. The four-class latent class analysis (LCA) used eight questionnaire-derived indicators of device use. Regression models evaluated exploratory cross-sectional associations with AL and high myopia, adjusting for demographic, familial, sleep and school covariates. RESULTS: LCA identified four phenotypes differing by screen purpose, weekday-weekend patterns, viewing distance and visual-break behaviour. The entertainment-dominant, weekend-heavy phenotype (11.5%) had the highest entertainment ratio and weekend concentration. The lower-screen, study-oriented phenotype (15.4%) had the lowest total screen time and the highest study ratio. Adjusted AL point estimates relative to the reference phenotype ranged from -0.25 to -0.02 mm. The lower-screen, study-oriented phenotype had nominally higher odds of high myopia (adjusted odds ratio = 1.90; 95% CI, 1.06 to 3.39; p = 0.03). This association was attenuated in the attention-check-correct subset. Mean AL was 24.83 ± 1.20 mm; mean worse-eye spherical equivalent was -3.35 ± 2.36 D and 115 students (12.8%) had high myopia. CONCLUSIONS: Four digital eye-behaviour phenotypes captured multidimensional exposure heterogeneity beyond total duration. These profiles provide a framework for prospective studies of whether behaviour combinations relate to refractive development beyond total duration.