Purpose: To investigate a possible relationship between refractive error and cognitive function.
Methods: This population-based, cross-sectional study included 1032 persons aged 60 to 79 who participated in the Singapore Malay Eye Study. Refraction (sphere, cylinder, and axis) was measured using an autorefractor, and spherical equivalent was defined as sphere plus half negative cylinder. Refractive errors were defined as myopia (spherical equivalent < -0.5), emmetropia (-0.5 diopter [D] ≤ spherical equivalent ≤ 0.5 D), and hyperopia (spherical equivalent > 0.5 D). Visual acuity was measured with a logMAR chart. Cognitive dysfunction, assessed using the Abbreviated Mental Test, was defined based on education-specific cutoff values.
Results: Compared with individuals with emmetropia, persons with myopia were almost twice as likely to have cognitive dysfunction (odds ratio 1.82; 95% confidence interval 1.05-3.15), after adjusting for age, sex, body mass index, income, education, and hours of reading and writing per day. Hyperopia was not associated with cognitive dysfunction. The association remained significant after further adjustment for uncorrected refractive errors or best-corrected visual acuity.
Conclusions: Our results provide evidence on a novel association between myopia and cognitive dysfunction.