Parapapillary Beta Zone in Primary School Children in Beijing: Associations With Outdoor Activity

PURPOSE. To investigate prevalence and size of parapapillary alpha zone and beta zone and associations with myopia-related factors in primary school children in Beijing. METHODS. The school-based study included 382 grade-1 children and 299 grade-4 children. The children underwent a comprehensive eye examination and the parents, an interview. The examination was repeated after 1 year. RESULTS. Beta zone (prevalence: 44.5% +/- 2.1%; mean area: 0.17 +/- 0.29 mm(2)) was significantly associated with more time spent indoors with studying (P = 0.004; standardized correlation coefficient beta: 0.14; regression coefficient B: 0.05; 95% confidence interval [CI]: 0.02, 0.09) after adjusting for longer axial length (P < 0.001; beta: 0.22; B: 0.07; 95% CI: 0.04, 0.10), more myopic refractive error (P < 0.001; beta: -0.29; B: -0.07; 95% CI: -0.09, -0.04), region of habitation (P -0.03; beta: 0.11; B: 0.07; 95% CI: 0.01, 0.14), and vertical disc diameter (P = 0.03; beta: 0.10; B: 0.16; 95% CI: 0.02, 0.30). As a corollary, indoors studying time was associated with larger area of beta zone (P = 0.01; beta: 0.11; B: 0.30; 95% CI: 0.07, 0.54) after adjusting for higher axial length/corneal curvature radius ratio (AL/CC; P = 0.006; beta: 0.12; B: 0.94; 95% CI: 0.27, 1.62) and urban region of habitation (P < 0.001; beta: -0.44; B: -0.75; 95% CI: -0.89, -0.61). An increase in AL/CC ratio at 1-year follow-up was associated with more indoors studying time (P = 0.04; beta: 0.10; B: 0.01; 95% CI: 0.00, 0.01) and larger beta zone area (P < 0.001; beta: 0.19; B: 0.04; 95% CI: 0.02, 0.05) after adjusting for axial length (P < 0.001; beta: -0.21; B: -0.01; 95% CI: -0.02, -0.01). CONCLUSIONS. Larger parapapillary beta zone area was associated with more indoors studying time after adjustment for axial length, refractive error, and region of habitation, and reversely, more indoors studying time was associated with larger beta zone in multivariate analysis. The results could indicate that parapapillary beta zone is associated with external factorsdependent development of myopia.