Prevalence of refractive errors under cycloplegia and associated factors with focus on the myopia epidemic among public school children from southern Brazil

Abstract

Objectives: Little information about the prevalence of myopia in Latin America is available and this study aims to detect the prevalence of refractive errors under cycloplegia in Southern Brazil. Main goal is prevalence of myopia, including the classification in pre-myopia, low myopia and high myopia and associated risk factors. Secondary objective is to describe the prevalence of hyperopia and astigmatism and compare them to the same variables as myopia. Materials and methods: A prospective cross sectional convenient sampling recruited 330 public school children between 2020 and 2021, aged 5 to 20 years old. All children underwent a comprehensive eye examination including cycloplegia and a detailed lifestyle questionnaire was applied. Results: Prevalence of myopia was 17.4% (Confidence Interval (CI) 13.8-21.7%). Low myopia (-0.50 D to -5.75 D) was 15.2% (CI 11.9-19.3%) and high myopia (-6.00 D or worse) was 2.1% (CI 1.1-4.1%). The prevalence of hyperopia was 7.7% (CI 5.4-10.9%) and of astigmatism, either myopic, mixed or hyperopic, was 25.6% (CI 21.4-30.2%). The relationship between refractive errors and sex, ethnicity, age, time of electronics use/daily, axial length and corneal Kmax are presented and compared among myopia, hyperopia and astigmatism. Data on pre-myopia is also disclosed. Median, asymmetry and kurtosis were applied. Conclusion: There is a correlation of myopia with sex, ethnicity, age and time of electronics use daily. Astigmatism was more prevalent in males and hyperopia had a higher magnitude in males too, but no association with ethnicity and electronics use was identified. This is the highest reported prevalence of myopia under cycloplegia in Brazil to date and Brazilian school children seem to be less hyperopic than in ancient publications, which represent a new reality in refractive errors distribution in the country.