Time Outdoors in Reducing Myopia: A School-Based Cluster Randomized Trial with Objective Monitoring of Outdoor Time and Light Intensity

Xiangui He; Padmaja Sankaridurg; Jingjing Wang; Jun Chen; Thomas Naduvilath; Mingguang He; Zhuoting Zhu; Wayne Li; Ian G Morgan; Shuyu Xiong; Jianfeng Zhu; Haidong Zou; Kathryn A Rose; Bo Zhang; Rebecca Weng; Serge Resnikoff; Xun Xu

doi:10.1016/j.ophtha.2022.06.024

Time Outdoors in Reducing Myopia: A School-Based Cluster Randomized Trial with Objective Monitoring of Outdoor Time and Light Intensity

Ophthalmology. 2022 Nov;129(11):1245-1254. doi: 10.1016/j.ophtha.2022.06.024. Epub 2022 Jun 30.

Authors

Xiangui He¹, Padmaja Sankaridurg², Jingjing Wang³, Jun Chen³, Thomas Naduvilath², Mingguang He⁴, Zhuoting Zhu⁵, Wayne Li², Ian G Morgan⁶, Shuyu Xiong⁷, Jianfeng Zhu³, Haidong Zou¹, Kathryn A Rose⁸, Bo Zhang³, Rebecca Weng², Serge Resnikoff², Xun Xu⁹

Affiliations

¹ Shanghai Eye Disease Prevention and Treatment Center, Shanghai Eye Hospital, Shanghai Vision Health Center & Shanghai Children Myopia Institute, Shanghai, China; Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University, National Clinical Research Center for Eye Diseases, Center of Eye Shanghai Key Laboratory of Ocular Fundus Diseases, Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai, China.
² Brien Holden Vision Institute, Sydney, Australia; School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
³ Shanghai Eye Disease Prevention and Treatment Center, Shanghai Eye Hospital, Shanghai Vision Health Center & Shanghai Children Myopia Institute, Shanghai, China.
⁴ Centre for Eye Research Australia; Ophthalmology, University of Melbourne, Melbourne, Australia; State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
⁵ Centre for Eye Research Australia; Ophthalmology, University of Melbourne, Melbourne, Australia.
⁶ Division of Biochemistry and Molecular Biology, Research School of Biology, Australian National University, Canberra, ACT, Australia.
⁷ Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University, National Clinical Research Center for Eye Diseases, Center of Eye Shanghai Key Laboratory of Ocular Fundus Diseases, Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai, China.
⁸ Discipline of Orthoptics, Graduate School of Health, University of Technology Sydney, Ultimo, NSW, Australia.
⁹ Shanghai Eye Disease Prevention and Treatment Center, Shanghai Eye Hospital, Shanghai Vision Health Center & Shanghai Children Myopia Institute, Shanghai, China; Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University, National Clinical Research Center for Eye Diseases, Center of Eye Shanghai Key Laboratory of Ocular Fundus Diseases, Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai, China. Electronic address: drxuxun@sjtu.edu.cn.

PMID: 35779695
DOI: 10.1016/j.ophtha.2022.06.024

Abstract

Purpose: To evaluate the efficacy of time outdoors per school day over 2 years on myopia onset and shift.

Design: A prospective, cluster-randomized, examiner-masked, 3-arm trial.

Participants: A total of 6295 students aged 6 to 9 years from 24 primary schools in Shanghai, China, stratified and randomized by school in a 1:1:1 ratio to control (n = 2037), test I (n = 2329), or test II (n = 1929) group.

Methods: An additional 40 or 80 minutes of outdoor time was allocated to each school day for test I and II groups. Children in the control group continued their habitual outdoor time. Objective monitoring of outdoor and indoor time and light intensity each day was measured with a wrist-worn wearable during the second-year follow-up.

Main outcome measures: The 2-year cumulative incidence of myopia (defined as cycloplegic spherical equivalent [SE] of ≤-0.5 diopters [D] in the right eye) among the students without myopia at baseline and changes in SE and axial length (AL) after 2 years.

Results: The unadjusted 2-year cumulative incidence of myopia was 24.9%, 20.6%, and 23.8% for control, test I, and II groups, respectively. The adjusted incidence decreased by 16% (incidence risk ratio [IRR], 0.84; 95% confidence interval [CI], 0.72-0.99; P = 0.035) in test I and 11% (IRR = 0.89; 95% CI, 0.79-0.99; P = 0.041) in test II when compared with the control group. The test groups showed less myopic shift and axial elongation compared with the control group (test I: -0.84 D and 0.55 mm, test II: -0.91 D and 0.57 mm, control: -1.04 D and 0.65 mm). There was no significant difference in the adjusted incidence of myopia and myopic shift between the 2 test groups. The test groups had similar outdoor time and light intensity (test I: 127 ± 30 minutes/day and 3557 ± 970 lux/minute; test II: 127 ± 26 minutes/day and 3662 ± 803 lux/minute) but significantly more outdoor time and higher light intensity compared with the control group (106 ± 27 minutes/day and 2984 ± 806 lux/minute). Daily outdoor time of 120 to 150 minutes at 5000 lux/minutes or cumulative outdoor light intensity of 600 000 to 750 000 lux significantly reduced the IRR by 15%～ 24%.

Conclusions: Increasing outdoor time reduced the risk of myopia onset and myopic shifts, especially in nonmyopic children. The protective effect of outdoor time was related to the duration of exposure and light intensity. The dose-response effect between test I and test II was not observed probably because of insufficient outdoor time achieved in the test groups, which suggests that proper monitoring on the compliance on outdoor intervention is critical if one wants to see the protective effect.

Trial registration: ClinicalTrials.gov NCT02980445.

Keywords: Children; Cluster randomized trial; Myopia; Outdoor; School health.

Publication types

Randomized Controlled Trial
Research Support, Non-U.S. Gov't

MeSH terms

Child
China / epidemiology
Humans
Mydriatics*
Myopia* / epidemiology
Myopia* / etiology
Myopia* / prevention & control
Prospective Studies
Refraction, Ocular
Schools

Substances

Mydriatics

Associated data

ClinicalTrials.gov/NCT02980445