Prevalence and associations of myopia in Hong Kong primary school students

Abstract

Purpose: To examine the prevalence of myopia in primary school children in Hong Kong, and the risk factors for myopia development.

Study design: A cross-sectional study.

Methods: Subjective refraction and axial length were measured in all participants. Structured questionnaire was completed by the parents to assess risk factors of myopia.

Results: A total of 1396 children (491 boys) from Grade 1 to Grade 6 from 4 primary schools in Sham Shui Po district of Hong Kong participated. All participants underwent non-cycloplegic refraction. The overall prevalence of myopia (spherical equivalent, SE ≤ -0.5 diopter [D]) was 37.7%, which significantly increased with age, from 13.3% at grade 1 to 54.7% at grade 6. The prevalence of moderate myopia (-3.0D < SE < -6.0D) increased from 1.6% at grade 1 to 18.2% at grade 6 and the prevalence of high myopia (SE < = -6.0 D and/or AL ≥ 26.5 mm) increased from 0.94% (7/747) in grade 1-3 students to 1.85% (12/649) in grade 4-6 students. Among the students with myopia, only 23.6% of the parents knew their children had refractive errors and only 19.8% of the children wore glasses. Multivariate logistic regression analysis showed myopia development was significantly associated with older age (OR = 1.36, P = 0.008), better academic ranking in class in the preceding semester (OR = 1.01, P = 0.02) and absence of routine eye check (OR = 2.70, P = 0.001).

Conclusion: The prevalence of myopia in primary school students in Hong Kong is high. There is a low level of awareness of refractive errors among parents, and high proportion of under-correction, resulting in suboptimal vision.