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PurposeTo investigate factors associated with ocular axial elongation and myopia progression during a 4-year follow-up in primary school children in Beijing.MethodsThis school-based study included 382 grade-1 children at baseline in 2011 (age:6.3±0.4 years) with 305 (79.8%) returning for the follow-up examination in 2015. At baseline and in yearly follow-up examinations, the children underwent a comprehensive eye examination including auto-refractometry, ocular biometry with measurement of axial length, and fundus photography. The parents underwent a standardized interview.ResultsDuring the study period, the mean axial length elongated by 1.15±0.56mm in boys and 1.10±0.63mm in girls. At baseline and at the end of follow-up, axial length was significantly (P<0.001) longer in boys, with no difference (P = 0.50) between genders in axial elongation. In multivariate analysis, greater axial elongation was associated (regression coefficient r2:0.15) with less time spent outdoors (P = 0.004; standardized coefficient beta: -0.22), more time spent indoors with studying (P = 0.02; beta: 0.18) and paternal myopia (P = 0.03; beta: 0.16). Larger increases in the axial length/anterior corneal curvature (AL/CC) ratio were associated (r2:0.09) with less time spent outdoors (PP = 0.003; beta: -0.22) and maternal myopia (PP = 0.02; beta: 0.18).ConclusionsMyopic axial elongation during a 4-year follow-up was associated with shorter time spent outdoors and longer time spent indoors studying and with parental myopia. Other factors such as level of paternal education, family income, gender and region of habitation were significantly associated with axial elongation and with myopia progression only in univariate analysis.

PurposeTo assess whether a change in myopia related oculometric parameters of primary school children in Beijing was associated with indoors and outdoors activity.MethodsThe longitudinal school-based study included school children who were examined in 2011 and who were re-examined in 2012. The children underwent a comprehensive eye examination including ocular biometry by optical low-coherence reflectometry and non-cycloplegic refractometry. Parents and children had a detailed interview including questions on time spent indoors and outdoors.ResultsOut of 681 students examined at baseline, 643 (94.4%) returned for follow-up examination. Within the one-year period, mean time spent daily outdoors increased by 0.4±0.9 hours, mean axial length by 0.26±0.49 mm, the ratio of axial length divided by anterior corneal curvature (AL/CC) by 0.03±0.06, and myopic refractive error by −0.06±0.89 diopters. In multivariate analysis, elongation of axial length was significantly associated with less total time spent outdoors (P = 0.02; standardized coefficient beta −0.12) and more time spent indoors with studying (P = 0.007; beta: 0.14) after adjustment for maternal myopia (P = 0.02; beta: 0.12). An increase in AL/CC was significantly associated with less time spent outdoors (P = 0.01; beta:−0.12) after adjustment for paternal myopia (P = 0.003; beta: 0.15) and if region of habitation was excludedors for leisure (P = 0.006; beta:−0.13), with less total time spent outdoors (P = 0.04; beta:−0.10), or with more time spent i. An increase in myopic refractive error, after adjustment for age, was significantly associated with less time spent outdo ndoors with studying (P = 0.005; beta: 0.13).ConclusionsA change in oculometric parameters indicating an increase in myopia was significantly associated with less time spent outdoors and more time spent indoors in school children in Greater Beijing within a study period of one year. Our study provides additional information on the potentially helpful role of outdoors activity in the prevention of myopia. Public health care measures such as school agendas may potentially take it into account.