Epidemiology of myopia

Abstract

Myopia is one of the most prevalent disorders of the eye. Higher myopia is associated with comorbidities that increase risks of severe and irreversible loss of vision, such as retinal detachment, subretinal neovascularization, dense cataract, and glaucoma. In recent years, reports from population-based prevalence studies carried out in various geographical areas now give a clear picture of the current distribution of refractive error. The scarcity of data from well-designed longitudinal cohort studies is still yet to be addressed. These studies have confirmed the previous data indicating that prevalence of refractive error varies according to ethnicity and geographic regions, and also point to an increase in myopia prevalence over the past half-century. The problem is particularly pronounced in affluent, industrialised areas of East Asia. Environmental risk factors for myopia related to socioeconomic status and lifestyle have been identified. The past decade has seen a greater understanding of the molecular biological mechanisms that determine refractive error, giving further support to the belief that myopia is the result of a complex interaction between genetic predisposition and environmental exposures. This review summarizes data on the prevalence, incidence, progression, associations, risk factors, and impact from recent epidemiological studies on myopia.

Figure 1

Determinants of refraction in adult Singaporeans. This graph shows cross-sectional data for mean axial length (AL) and mean LOCS nuclear opacity (NO) lens grade in a Chinese Singaporean population aged 40–82 years. NO grade increases linearly with age, whereas there is a clear pattern for axial length to be longer in younger people. The AL differences presumably reflect a cohort effect with each age-group having static, lifelong differences in axial length, rather than indicating an age-related decline in AL. The population % myopia is shown in overlay, and appears to show a greater effect of AL on refractive status in people aged 40–59 years. From the age of 60, the impact of nuclear opacity grade (NO) increases, resulting in a greater impact of ‘index myopia'.