Abstract
Purpose :
Time outdoors is known to have a protective effect on myopia. It is unknown if progression of myopia is inhibited by time spent outdoors over a long period of time. The objective of this study is to assess the relationship between time spent outdoors at 6 years and axial length, axial length elongation and risk of myopia at 6, 9 and 13 years of age.
Methods :
Children from the population-based birth cohort study Generation R underwent ocular biometry measurements with AL at ages 6.2 (N = 6321), 9.9 (N = 5430) and 13.6 (N= 4851) years of age, with measurements of objective cycloplegic refractive error at 9 and 13 years (N=2462 and N=3086). Myopia was defined as mean SER of ≤-0.5D in both eyes. Time spent outdoors was assessed at 6 years with a questionnaire. Association between time spent outdoors and axial length was examined with linear regression. Risk of myopia was determined with logistic regression. Analyses were adjusted for age, gender and ethnicity.
Results :
Axial length was on average 22.36 (0.75) mm, 23.10 (0.84) mm, and 23.50 (0.95) mm at 6, 9 and 13 years of age respectively. Children spent on average 1.60 (±1.17) hours/day outdoors at 6 years and ±1.23 (1.05) at 9 years. The correlation between time spent outdoors at 6 years and 9 years was 0.26 (P < 0.001) Axial length showed a significant association with time spent outdoors at 6 years (-0.035 ± 0.009) 9 years (-0.055 ± 0.011 ) and 13 years (-0.061 ± 0.014) (all P < 0.001). Children who spent more time outdoors at 6 years had slower axial length elongation 6 to 9 years (-0.005 ± 0.001 P <0.001), and 9 to 13 years (-0.003±0.001 P = 0.007). More time spent outdoors at 9 years was associated with shorter axial length (-0.025±0.012 P=0.025) at 9 years and (-0.045±0.015 P=0.003) at 13 years. Children who spent more time outdoors at 9 years had slower axial length elongation between 9 and 13 years (-0.004 ± 0.001 P <0.001). Risk of myopia decreased per hour per day outdoors at 6 (OR 0.63; P <0.001), at 9 years (OR 0.78; P = 0.003) and a 13 years (OR 0.84; P =<0.001).
Conclusions :
Children who spent less time outdoors had faster axial length growth in the years after and also progressed faster after the age of 10 years. This is important for myopia management as time spent outdoors is a healthy habit with many advantages and negligible side effects.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.