Purpose To investigate the relationship between seasonal variation of daylight length and spherical equivalent (SE) progression among the schoolchildren participating in the Myopia Investigation Study in Taipei.
Methods We used the first-year data from grade 2 schoolchildren who completed all the baseline and two follow-up examinations (n=6790). There were two 6-month intervals between visits over winter and summer, respectively. For each interval, we calculated average daily daylight length using data from Taiwan’s Central Weather Bureau and measured 6-month SE progression rate based on right eye cycloplegic autorefraction data. The midpoint month was defined as the month midway between two consecutive visits.
Results By the midpoint month, average daily daylight length was the shortest in December (671±7 min/day) and the longest (785±7 min/day) in June, and SE progression rate was the fastest (−0.23±0.48 D) in December and the slowest (−0.17±0.51 D) in June. Significant variation of SE progression rate with season can be observed only among the schoolchildren (n=1905) whose midpoint months for the winter and summer intervals were December and June (winter rate, −0.25±0.47 D; summer rate, −0.17±0.49 D; p<0.001). Of those, the summer progression rate was approximately 80%, 65% and 61.5% of that measured in winter for myopic (p=0.252), emmetropic (p=0.012) and hyperopic (p=0.012) schoolchildren, respectively.
Conclusion Our data demonstrate a seasonal variation of minus shift in refractive error among Taipei schoolchildren who had significant daytime fluctuation during the 1-year follow-up. Of those, non-myopic children had significant and more pronounced variation of SE progression than myopic children.
- child health (paediatrics)
- optics and refraction
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D-CT and CJ-LL contributed equally.
Funding The present study was supported by grants H10237 and P10303 from the Taipei City Government.
Disclaimer The interpretation and conclusions contained herein do not represent those of the Department of Health, Taipei City Government or Databank for Public Health Analysis.
Competing interests None declared
Ethics approval The Institutional Review Board of the Taipei City Hospital (TCHIRB-1020501).
Provenance and peer review Not commissioned; externally peer reviewed.
Patient consent Parental/guardian consent obtained.
Contributors Study conception and design: D-CT, NH, AW-HC and CJ-LL. Data acquisition: NH, C-CH, P-YL, S-YC, Y-ML, AW-HC and CJ-LL. Analysis and interpretation of data: D-CT, NH, S-YF and CJ-LL. Drafting or revising the article: D-CT, NH, Y-ML and CJ-LL. Final approval: all authors. Overall responsibility: D-CT and CJ-LL.
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