Variation in prevalence of myopia between generations of migrant indians living in Singapore

Purpose: To assess the influence of factors related to migration and acculturation on myopia in migrant Indians in Singapore.

Design: Population-based cross-sectional study.

Methods: A total of 3400 Singaporean Indians (75.6% response rate) aged over 40 years participated in this study. Information regarding country of birth, migration age, and language of interview were collected from interviews. Indians born outside of Singapore were defined as "first-generation" immigrants, while Indians born in Singapore were defined as "second-generation (or higher)" immigrants. Refraction was determined by autorefraction and refined by subjective refraction. Ocular biometry including axial length (AL), anterior chamber depth (ACD), and corneal radius (CR) were measured by partial coherence interferometry. Myopia and high myopia were defined as spherical equivalents (SE) of less than -0.5 diopter (D) for myopia, and < -5 D for high myopia, respectively.

Results: The prevalence of myopia (30.2% vs 23.4 %) and high myopia (4.8% vs 2.5%) were higher in second-generation immigrants compared with first-generation immigrants. Second-generation immigrants had longer AL (23.50 mm vs 23.37 mm, P = .004) than first-generation immigrants after multivariate adjustment. The excess prevalence of myopia was reduced by 37.5% but remained statistically significant (P = .02) after further controlling for educational level. Among first-generation immigrants, those migrating to Singapore before the age of 21 had significantly higher prevalence of myopia (odds ratio [OR]: 1.85; 95% confidence interval [CI]: 1.32, 2.59) and longer AL (regression coefficient: 0.27; 95% CI: 0.11, 0.43) than those migrating after 21 years of age. Also, first-generation immigrants interviewed in English had higher prevalence of myopia (OR: 1.46; 95% CI: 1.00, 2.17) than their non-English-interviewed counterparts.

Conclusions: The prevalence of myopia among second-generation (or higher) Indian immigrants in Singapore is higher than first-generation immigrants. Country-specific environmental factors may be important for the increasing prevalence of myopia in Asia.