Optic disc-fovea distance and myopia progression in school children: the Beijing Children Eye Study

PURPOSE: To assess changes in the optic disc-fovea distance (DFD) with progressing myopia in school children. METHODS: The school-based, prospective, longitudinal study included grade-1 children in 2011 who were yearly re-examined until 2016. We measured DFD, optic disc diameters and width of parapapillary gamma zone (parapapillary region without Bruch's membrane (BM)) on fundus photographs. RESULTS: Of 382 grade-1 children examined in 2011, 294 (77.0%) children (mean age in 2011: 6.4 ± 0.5 years) returned to be examined in 2016. In relative terms, the increase in DFD (1.15 ± 0.33 mm) was more due to an increase in gamma zone width (+300% or 0.29 ± 0.30 mm) than an increase in macular BM length (+18% or 0.74 ± 0.21 mm). In multivariate regression analysis, longer increase in DFD was correlated (regression coefficient r2  = 0.79) with longer axial elongation during the study period (p < 0.001; standardized regression coefficient β: 0.61; non-standardized regression coefficient B: 0.30; 95% confidence interval (CI): 0.26, 0.33), larger increase in gamma zone width (p < 0.001; β: 0.35; B: 0.40; 95%CI: 0.32, 0.48) and longer axial length in 2011 (p = 0.01; β:0.07; B:0.03; 95%CI:0.01, 0.06). Larger increase in gamma zone width was associated (r2  = 0.73) with larger increase in DFD (p < 0.001; β: 0.51; B: 0.46; 95%CI: 0.39, 0.53), larger increase in the vertical-to-horizontal disc diameter ratio (p < 0.001; β: 0.43; B:1.21; 95%CI: 1.00, 1.42) and longer vertical disc diameter (p < 0.001; β: 0.15; B:0.24; 95%CI: 0.14, 0.34). CONCLUSION: In adolescent school children, axial elongation-associated increase in DFD was mainly due to an enlargement (+300%) of parapapillary gamma zone, while macular BM length increased to minor degree (+18%). Gamma zone enlargement was correlated with axial elongation-associated vertical optic disc rotation, potentially due to an increased backward pull of the optic nerve on the temporal optic disc border.