Factors associated with the high prevalence of myopia and its decrease-A historical review.

Abstract

Purpose: To review historical and recent studies on the epidemiology of myopia, identify the factors associated with its prevalence and determine how myopia has been successfully prevented.

Methods: Historical and recent publications were reviewed regarding factors associated with the prevalence of myopia and the success of myopia prevention. Among the historical studies, Herman Cohn's studies in Germany and Johan Widmark's studies in Sweden were referenced and compared.

Results: In the 1800s, the prevalence of myopia caused by school glasses was high in the upper grades of many schools in Germany and Sweden. In Germany, the mean prevalence of myopia in the upper grades of 24 schools was 58%, exceeding 70% in several schools. At the same time in Sweden, the corresponding average prevalence was 45%, with the highest prevalence of 65%. Germany and Sweden implemented several generally accepted reforms to reduce the educational burden of schooling. Widmark compared the prevalence of myopia in the same schools in Sweden between the periods 1822-1883 and 1904-1905. The mean myopia prevalence decreased from 22.2% to 9.8%, and from 45.3% to 17.4% in the highest grades of these schools. Widmark identified three factors to explain the decrease in myopia prevalence: (1) improved lighting due to electric lights; (2) Fraktur fonts in schools were replaced by Antiqua; and (3) the number of outdoor activities was increased. The discussion aims to find similarities between Cohn's and Widmark's studies and the current myopia boom and to describe how these historical observations might currently be used to prevent myopia.

Conclusion: Myopia generally begins after starting school. The younger the children are subjected to the strain caused by near work and the less time spent outdoors at school, the higher the prevalence of myopia and the higher the myopia in adulthood. To control the current myopia boom in countries where the prevalence is highest, major changes should be implemented in the education system to reduce the need for near work and increase the time children spend outdoors.