Design and methodology of the Shanghai child and adolescent large-scale eye study (SCALE)

ImportanceNearly half of children suffering vision impairment reside in China with myopia accounting for the vast majority. BackgroundTo describe the design and methodology of the Shanghai Child and Adolescent Large-scale Eye Study (SCALE). DesignThe SCALE was a city wide, school-based, prospective survey. ParticipantsChildren and adolescents aged 4-14years from kindergarten (middle and senior), primary schools and junior high schools of all 17 districts and counties of the city of Shanghai, China were examined in 2012-2013. MethodsEach enrolled child underwent vision assessment (distance visual acuity; uncorrected and with corrective device if worn) and their parent/carer completed a questionnaire designed to elicit risk factors associated with myopia. Additionally, non-cycloplegic autorefraction and ocular axial length was measured in a subset of the larger sample. Main Outcome MeasuresPrevalence and the associated factors of vision impairment, myopia and high myopia in Shanghai. ResultsIn 2012-2013, a total of 910245 of the eligible 1196763 children and adolescents identified from census (76%, mean age 9.02.7years [4-14years]) were enrolled with visual acuity screened in the city of Shanghai. Of these, 610952 children (67% of the entire sample) underwent non-cycloplegic autorefraction and 219188 (24% of the entire sample) had both non-cycloplegic autorefraction and axial length measurements. Conclusions and RelevanceThe study results will provide insights on the burden of vision impairment, myopia and high myopia in children and adolescents in a metropolitan area of China, and contribute to the policies and strategies to address and limit the burden.