Refractive errors in an elderly rural Japanese population: The Kumejima study

Area of Science:

• Ophthalmology
• Public Health
• Epidemiology

Background:

• Refractive errors significantly impact visual function, ocular health, and quality of life.
• Prevalence of refractive errors varies globally, with high myopia reported in urban Japan.
• A rural Japanese island (Kumejima) with high glaucoma rates was chosen to assess refractive conditions.

Purpose of the Study:

• To determine the prevalence of myopia, high myopia, hyperopia, astigmatism, and anisometropia in a rural Japanese population.
• To analyze the relationship between age and refractive error types.
• To compare refractive error prevalence with other global populations and an urban Japanese cohort.

Main Methods:

• Cross-sectional study assessing refractive conditions on Kumejima island.
• Defined myopia (SE < -0.5 D), high myopia (SE < -5 D), hyperopia (SE > +0.5 D), astigmatism (cylinder > 0.5 D), and anisometropia (SE difference > 1.0 D).
• Age-specific prevalence rates and comparisons with other populations were analyzed.

Main Results:

• Prevalence rates in Kumejima: myopia 29.5%, high myopia 1.9%, hyperopia 34.1%, astigmatism 38.8%, anisometropia 15.5%.
• Myopia prevalence decreased with age until 70, then slightly increased; hyperopia increased until 70 and plateaued.
• Astigmatism and anisometropia were more prevalent in older individuals. Myopia rates were lower than urban Japan but higher than many other ethnic groups.

Conclusions:

• Rural Kumejima exhibits distinct refractive error patterns, notably high hyperopia and astigmatism.
• Age influences refractive error distribution, with specific trends for myopia and hyperopia.
• The high prevalence of hyperopia may correlate with the island's high rate of angle-closure glaucoma.