Purpose: To evaluate the prevalence of refractive errors associated with age, gender, and central corneal thickness and to evaluate astigmatism in the refraction and keratometry in a randomly sampled elderly Japanese population.
Design: Population-based epidemiologic survey.
Participants: A random sampling of residents of Tajimi, Japan, aged 40 years or older. A total of 3021 residents (participation rate, 78.1%) participated.
Methods: Each subject underwent screening examinations including autokeratorefractometry, subjective refraction, best-corrected visual acuity, central corneal thickness measurement, intraocular pressure measurement, slit-lamp examination, fundus photography, and visual field testing.
Main outcome measures: The prevalence of myopia (spherical equivalent [SE], <-0.5 diopters [D]), high myopia (SE, <-5 D), hyperopia (SE, >0.5 D), refractive astigmatism (cylinder, >0.5 D), and anisometropia (difference in SE between eyes, >1.0 D), and the correlation of refractive errors with age, gender, and central corneal thickness. Astigmatism in the refraction and keratometry was analyzed using polar value analysis and the vector calculation method.
Results: The crude prevalence of myopia, high myopia, hyperopia, refractive astigmatism in the refraction, and anisometropia was 41.8% (95% confidence interval [CI], 40.0%-43.6%), 8.2% (95% CI, 7.2%-9.2%), 27.9% (95% CI, 26.3%-29.6%), 54.0% (95% CI, 52.1%-55.8%), and 15.1% (95% CI, 13.7%-16.4%), respectively. The prevalence of myopia decreased with age up to 70 to 79 years but increased slightly in patients 80 years and older; the prevalence of hyperopia showed the opposite trend. The prevalence of astigmatism and anisometropia was higher in the older age groups. No significant gender difference was found associated with the refractive status except for keratometric readings. Polar value analysis and the vector calculation method showed a trend toward against-the-rule astigmatism with increasing age in both refractive and keratometric astigmatism, with a discrepancy between the two.
Conclusions: The overall prevalence of myopia (SE, <-0.5 diopters) was 41.8% in the study population, which is higher than that in population-based studies previously reported.