Prevalence and associated factors of myopia among rural school students in Chia-Yi, Taiwan

Background: The prevalence of myopia has increased rapidly worldwide over the past few decades. The aim of this study was to evaluate the prevalence and associated risk factors for myopia in elementary and junior high school students in Chia-Yi, Taiwan.

Methods: We included 5417 students in total from Grade 1-6 (n = 4763) and Grade 7-9 (n = 654) from Chia Yi County in this population-based study. The students underwent noncycloplegic autorefractometry and an interview with a structured questionnaire.

Results: For this study population, the prevalence of myopia and high myopia was 42.0 and 2.0%, respectively, revealing a statistically significant increase with increasing age (p < 0.05). Junior high school students (aged 13-15) showed a greater prevalence of myopia than elementary school students (aged 7-12) (55.8% vs. 40.1%, respectively, p < 0.001). Multiple logistic regression analysis showed that associated factors of myopia were body height (odds ratio [OR]: 1.05, 95% confidence interval [CI]: 1.05-1.06), body mass index (OR: 0.98, 95% CI: 0.96-1.00), and ocular alignment (horizontal heterophoria vs. orthophoria, OR: 2.37, 95% CI: 2.08-2.70; tropia vs. orthophoria, OR: 1.94, 95% CI: 1.50-2.52) for elementary school students, whereas in junior high school students, they included body height (OR: 1.02, 95% CI: 1.01-1.04) and ocular alignment (heterophoria vs. orthophoria, OR: 2.20, 95% CI: 1.56-3.10).

Conclusions: This study provided epidemiological data on myopia in rural school students in Chia-Yi, Taiwan, and demonstrated the association between heterophoria and myopia. Correction of refractive errors in the students remained a challenge.

Keywords: Heterophoria; Myopia; Rural; School students; Taiwan.