Wang SK, et al. - Researchers ascertained the incidence of myopia and high myopia based on refraction without cycloplegia among children in primary and junior high schools in China. Findings suggested that of any cultural or ethnic group the highest incidence of myopia was seen in Chinese students based on refraction without cycloplegia. In Chinese populations, interventions to prevent myopia onset should be initiated in primary schools, if confirmed with cycloplegic refraction.

Methods

• Experts completed this observational cohort study in Guangzhou, China.
• It comprised 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.
• They randomly chose all the schools at rates proportional to the number of schools in each of the city’s 11 districts.
• Students in grade 1 (primary school) or grade 7 (junior high school) with or without myopia were eligible for inclusion.
• They conducted the data analysis from February 2017 to October 2017.
• They defined myopia 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.
• They defined the annual incidences as the proportion of participants each year found to have myopia or high myopia who did not previously have the condition.

Results

• Results demonstrated that 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.
• Findings suggested that 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.
• In grade 1 students, baseline prevalence of myopia was 12.0% (n=237 of 1969) and 67.4% in grade 7 students (n=1795 of 2663).
• Researchers noted that 20% to 30% was the incidence of myopia each year throughout both cohorts.
• They found that initially, the incidence of high myopia was 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%]).