[Analysis of secular trends in proportion of students with poor visual acuity and the associated factors according to government statistics].

PURPOSE: Statistics obtained by the Japanese government were analyzed with the aim of elucidating the recent secular trends in proportion of students with poor visual acuity and the associated factors.
METHODS: Data on the proportion of students with poor visual acuity were collected from the reports of the School Health Examination Surveys conducted from 1979 to 2012, and were graphically analyzed to detect a secular trend. We collected prefecture-level data regarding the visual acuity, body height, study time, sleeping duration, video-gaming duration, and duration of exposure to sunshine of sixth-grade students of elementary schools in all 47 prefectures in Japan. The relationship between poor visual acuity and other factors was explored by performing multiple regression analysis to identify the important predictors of poor visual acuity.
RESULTS: A temporary retarding phase in the increasing tendency, as a halt in the growing tendency in terms of height, was observed in a proportion of students with poor visual acuity. Poor visual acuity was negatively correlated with duration of exposure to sunshine and was positively correlated with body height, but was only slightly correlated with study time and video-gaming duration.
CONCLUSIONS: Because myopia is incriminated as the main cause of poor visual acuity, these results suggest that myopia progression would be influenced by the circumstances of exposure to light.