Elsevier

Survey of Ophthalmology

Volume 44, Supplement 1, October 1999, Pages S109-S115
Survey of Ophthalmology

Review
Prevalence of Myopia and Refractive Changes in Students From 3 to 17 Years of Age

https://doi.org/10.1016/S0039-6257(99)00094-6Get rights and content

Abstract

We investigated changes in the prevalence of myopia and mean changes in refractive errors in Japanese students from 3 to 17 years old from 1984 to 1996. Mass ophthalmologic surveys were performed annually during the course of the study. The age-specific frequency distribution of refractive errors remained similar for 6-year-old students (defined in this study as students in the first grade of primary school) during the 13-year period, but the distribution became gradually skewed toward myopia for 12-year-old students (defined in this study as students in the first grade of junior high school). Comparisons between 1984 and 1996 examinations showed a considerable increase in the incidence of myopia among those 7 years of age or older, and changes in mean refractive errors also demonstrated a greater shift toward myopia, especially in students older than 10 years, for whom the changes were statistically significant. In this 13-year period, the prevalence of myopia increased from 49.3% to 65.6% in 17-year-old students. In addition to the annual mass ophthalmologic examinations, we also performed a longitudinal 6-year study of 346 students who entered junior high school in 1989, 1990, or 1991. Among these students, the prevalence of myopia increased from 43.5% at 12 years of age to 66.0% at 17 years of age. These 346 students were divided into the following eight groups according to their refractive error (spherical power [D]) at 12 years of age: +1 D, 0 D, −1 D, −2 D, −3 D, −4 D, −5 D, and −6 D. Mean progressions of myopia in these students were as follows: for the +1 D group, −0.14 D/year; for the 0 D group, −0.25 D/year; for the −1 D group, −0.37 D/year; for the −2 D group, −0.40 D/year; for the −3 D group, −0.29 D/year; for the −4 D group, −0.25 D/year; for the −5 D group, −0.14 D/year; and for the −6 D group, −0.22 D/year. Boys and girls demonstrated a statistically significant difference in mean changes in refractive errors at the 6-year follow-up examination: the mean change in refractive error was −1.41 ± 1.25 D for boys as compared with −1.03 ± 1.07 D for girls (unpaired Student's t-test, P < 0.0001). Our results demonstrated an early age at onset for myopia and a recent increase in the proportion of myopic students. Further studies are needed to shed light on the extent to which myopia is caused by environmental factors, because it is through these factors that the prevalence rate may be affected.

Section snippets

Subjects and Methods

The subjects of our present study were all students in the same kindergarten, primary school, junior high school, and senior high school affiliated with the national universities in Nara, Japan. The school children were selected from a pool of applicants. Annual mass ophthalmologic examinations were conducted at the schools from 1984 to 1996 by the same examiners throughout the entire period, with the same methodology and criteria. The total numbers of examinees were as follows: 1,940

Results

The age-specific frequency distribution of refractive errors for 6-year-old students (defined in this study as students in the first grade of primary school) and for 12-year-old students (defined in this study as students in the first grade of junior high school) during the 13-year period is shown in Fig. 1A-M. For 6-year-old students, the +1 D group has a sharp curve with a peak, and no changes were observed in this distribution throughout our study. Conversely, for the 12-year-old students,

Discussion

The age-specific frequency distribution of refractive errors remained similar for 6-year-olds during the 13 years studied, but myopia gradually increased in the 12-year-olds. The incidence of myopia among students older than 7 years was greater in 1996 than in 1984. In this 13-year period, the prevalence of myopia increased from 49.3% to 65.6% in 17-year-olds. This dramatic increase in the prevalence of myopia may be related to changes in physique (i.e., the reported differences in the results

Acknowledgements

The authors have no proprietary interest in products or techniques described in this article.

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