Is Refractive Error Associated with Body Mass Index?

Abstract

Background: Refractive errors are a leading cause of visual impairment, and both myopia prevalence and obesity rates are increasing globally. Emerging literature suggests that body mass index (BMI) may be associated with refractive outcomes, but findings remain inconsistent. Objective: To synthesize evidence on the association between BMI and refractive errors, including myopia, astigmatism, and hyperopia/hyperopic reserve. Methods: A narrative review was conducted using PubMed/MEDLINE, Google Scholar, Scopus, and Web of Science to identify peer-reviewed observational studies published within the last ten years examining BMI and refractive outcomes. Keywords included body mass index, obesity, overweight, myopia, astigmatism, hyperopia, and refractive error. Findings were synthesized narratively due to heterogeneity in populations and outcome definitions. Results: The reviewed evidence, predominantly cross-sectional, most consistently linked BMI with myopia, including nonlinear (J-shaped or inverse L-shaped) patterns in large adolescent datasets. Associations appeared stronger for high myopia than for mild-to-moderate myopia in several populations. Astigmatism was also positively associated with higher BMI in adolescents and was supported by maternal BMI associations with offspring corneal curvature. Evidence for hyperopia prevalence was limited; however, higher BMI was associated with suspected insufficient hyperopic reserve in preschool children. Conclusion: Current evidence suggests that BMI is associated with myopia and astigmatism, while evidence for hyperopia remains inconclusive. Longitudinal studies with standardized refraction assessment and precise adiposity measures are required to clarify temporal relationships and biological mechanisms.