Myopia on the Rise Among Elementary and Junior High School Students―Myopia Found in 80% of Elementary and, 95% of Junior High School Students in Tokyo―
September 6, 2019
Keio University School of Medicine
A research team at the Keio University School of Medicine has conducted Japan’s first prevalence study on myopia in 20 years. Led by Professor Kazuo Tsubota of the Department of Ophthalmology, the study looked at approximately 1,400 elementary and junior high school students in the Tokyo area and found a possible correlation between myopia and dry eye. The team included Project Associate Professor Toshihide Kurihara, Instructor Hidemasa Torii, and fourth-year doctoral candidate Erisa Yotsukura.
In 2005, the Ministry of Health, Labor and Welfare reported that myopia was the fourth most common cause of blindness in Japan, yet despite the urgent need for myopia prevention, a study on the prevalence of myopia in children had not been conducted in Japan since the 1990s.
Myopia refers to a condition of the eye where light focuses in front of, rather than on, the retina, causing distant objects to appear blurry. Myopia is diagnosed using a refractive assessment, and is attributed to excessive axial elongation, which causes changes to the ocular shape and increases the distance from the cornea to the retina. Axial length elongates in children as they grow and is known to be particularly long in myopic eyes, making the accurate measurement of axial length increasingly important in evaluating myopia. With high myopia it is understood that as axial length elongates there is an increase in the risk of complications such as macular degeneration and optic nerve damage.
In this study, as an evaluation of myopia, the research group measured both refraction index (objective refraction values using a non-cycloplegic refraction technique) and axial length, and through a questionnaire investigated the relationship between myopia and lifestyle. Results showed that the prevalence of myopia in 689 elementary school students was 76.5%, while the prevalence of high myopia was 4.0%, and the average axial length was 23.41 mm. In 727 junior high school students, the prevalence of myopia was 94.9%, higher than existing reports abroad. The prevalence of high myopia was 11.3%, and the average axial length was 24.73 mm.
The results of this research represent a data set on the prevalence of myopia in Japan, including measurements of axial length, and provide the latest basic data in recent years on myopia in elementary and junior high school students in Tokyo. It is expected that these results will sound the alarm about the increasing prevalence of myopia and help raise awareness to stop the increasing prevalence of both myopia and high myopia.
The results of this study were published on August 15, 2019, in the online journal JAMA Ophthalmology.