Myopia Becoming More Common Among Chinese Children, Study Suggests
Incidence of and Factors Associated With Myopia and High Myopia in Chinese Children, Based on Refraction Without Cycloplegia
Question: What is the incidence of myopia and high myopia among school-aged students in China?
Findings: In this cohort study of 4741 Chinese children, the incidence of myopia was 20% to 30% each year from grade 1 to grade 6 and from grade 7 to grade 9 based on refraction without cycloplegia.
Meanings: The incidence of myopia among Chinese students determined by refraction without cycloplegia is among the highest of any cultural or ethnic group; if confirmed with cycloplegic refraction, the findings might support earlier interventions in this population.
Importance: Myopia has reached epidemic levels among children in regions of East and Southeast Asia. High myopia is associated with myopic macular degeneration, glaucoma, and retinal detachment.
Objective: To determine the incidence of myopia and high myopia based on refraction without cycloplegia among children in primary and junior high schools in China.
Design, Setting, and Participants: This observational cohort study was completed in Guangzhou, China. It consisted of a cohort from 19 primary schools, who were followed up from 2010 to 2015, and a cohort from 22 junior high schools, who were followed up from 2010 to 2012. All schools were randomly chosen at rates proportional to the number of schools in each of the city’s 11 districts. Students with or without myopia in grade 1 (primary school) or grade 7 (junior high school) were eligible for inclusion. Data analysis occurred from February 2017 to October 2017.
Main Outcomes and Measures: Myopia was defined as a spherical equivalent refraction (SER) of −0.50 diopters (D) or less, as measured by subjective refraction without cycloplegia; high myopia was defined as a SER of −6.0 D or less. Annual incidences were defined as the proportion of participants each year found to have myopia or high myopia who did not previously have the condition. Height, weight, axial length (AL), corneal radius of curvature (CRC), and AL/CRC ratio were examined to assess if these measures were associated with future myopia or high myopia.
Results: A total of 4741 students with or without myopia in either grade 1 for the primary school cohort (mean [SD] age 7.2 [0.4] years; 932 of 1975 [47.2%] female) or grade 7 for the junior high school cohort (mean [SD] age 13.2 [0.5] years; 1254 of 2670 [47.0%] female) were included. Baseline mean (SD) SER was 0.31 (0.86) D among 1975 students in grade 1 vs −1.60 (2.00) D among 2670 students in grade 7. Baseline prevalence of myopia was 12.0% in grade 1 students (n = 237 of 1969) and 67.4% in grade 7 students (n = 1795 of 2663). The incidence of myopia was 20% to 30% each year throughout both cohorts. The incidence of high myopia was initially less than 1% in the primary school cohort (grade 1: n = 2 of 1825; 0.1% [95% CI, 0.0%-0.3%]), but incidence exceeded 2% in the junior high school cohort (in grade 9: n = 48 of 2044; 2.3% [95% CI, 1.0%-3.7%]).
Conclusions and Relevance: The incidence of myopia among Chinese students based on refraction without cycloplegia is among the highest of any cultural or ethnic group. If confirmed with cycloplegic refraction, interventions to prevent myopia onset in Chinese populations should be initiated in primary schools.
Sean K. Wang, BS1,2; Yangfeng Guo3; Chimei Liao, MD1; et al Yanxian Chen, PhD1,4; Guangxing Su1; Guohui Zhang1; Lei Zhang, PhD5,6,7,8; Mingguang He, MD, PhD1,9
JAMA Ophthalmology. Published online July 5, 2018.