Shanghai Time Outside to Reduce Myopia trial: design and baseline data

Abstract

Importance: Myopia is a major public health concern worldwide, while outdoor time is indicated to be protective against the onset of myopia.

Background: To describe the methodology and baseline data of the Shanghai Time Outside to Reduce Myopia (STORM) trial.

Design: A 2-year, school-based, prospective, cluster randomized trial.

Participants: Children from grade I and II classes of 24 schools from eight districts in Shanghai, China, were randomized to either a control group, a test group I (40-min outdoor time/day) or test group II (80-min outdoor time/day).

Methods: At baseline and annual intervals, cycloplegic autorefraction and axial length measurement will be performed. Time outdoors and light exposure will be monitored via parent/carer questionnaires and a wearable device.

Main outcome measures: Spherical equivalent, prevalence of myopia and time outdoors in each group.

Results: A total of 6295 eligible children (age 7.2 ± 0.7 y [6-9 y]) were randomized to control (n = 2037), test group I (n = 2329) and test group II (n = 1929). At baseline, spherical equivalent was +0.98 ± 1.02D, +1.02 ± 1.02D and +1.00 ± 0.99D (P = 0.708), myopia prevalence was 8.9, 7.7 and 7.8% (P = 0.270) and time outdoors was 58.5 ± 35.8, 59.8 ± 34.7 and 58.5 ± 35.3 min/d (P = 0.886) for control, test groups I and II, respectively.

Conclusions and relevance: Myopia prevalence was high at nearly 8 to 9% in school children aged 7 years in Shanghai, China. The current trial will help evaluate if increased time outdoors has a role to play in reducing the incidence of myopia and/or slow the progression of myopia.

Keywords: children; intervention; myopia; outdoor; prevention.