PURPOSE. The purpose of this study was to assess the ovality of the optic disc and its associations with myopia-related factors in primary school children in Beijing. METHODS. This longitudinal school-based study included 382 grade 1 children and 299 grade 4 children who were followed for 2 years. Study participants underwent a comprehensive eye examination including autorefractometry, ocular biometry, and fundus photography. RESULTS. Fundus photographs were available for 562 children (82.5%). The mean optic disc ovality (maximal-to-minimal disc diameter) was 1.17 +/- 0.29 (range, 1.00-1.50). Oval discs defined by an ovality of >= 1.33 were detected in 37 children (prevalence: 6.6%; 95% confidence interval: 4.5-8.6). In multivariate linear regression analysis, higher optic disc ovality index was significantly associated with older age (P = 0.001), female sex (P = 0.005), larger parapapillary beta zone (P < 0.001), and shorter time spent indoors with studying (P = 0.003) and was marginally significant (P = 0.057), with greater increase in myopic refractive error from 2011 to 2013. From 2011 to 2013, myopic refractive error increased in the oval optic disc group by 1.03 +/- 0.99 diopters compared to 0.67 +/- 1.31 diopters in the nonoval disc group. CONCLUSIONS. The prevalence of oval optic discs in Beijing school children was markedly higher than in the elderly Beijing Eye Study population (6.6% vs. 0.36%), paralleling the higher prevalence of myopia in school children. The association between oval optic discs and less time spent indoors with studying after adjusting for longitudinal change in myopic refractive error, age, sex and parapapillary beta zone may warrant further exploration of external factors associated with oval optic discs.