The effect of the Chinese Cultural Revolution and Great Leap Forward on the prevalence of myopia

The Great Leap Forward was a campaign from 1958 to 1961 aiming to rapidly transform China from an agrarian economy into a modern industrialized communist society by the process of rapid industrialization and collectivization. It resulted in mass starvation in many provinces in China. The general disorganization and partial collapse of many parts of public life markedly affected the educational systems so that many schools were either closed or were open only part time. Also, many parents could not afford to send their children to school. After some years of economic re-growth, the Great Leap Forward was followed by the Cultural Revolution from 1966 to 1976. From the sudden start of the Cultural Revolution in 1966 onwards, schools were closed for 1–2 years. School education was only slowly re-institutionalized during the following period of 8 years until the Cultural Revolution ended in 1974. Myopia or shortsightedness is a potentially blinding disorder and has markedly gained in importance in China, since its prevalence profoundly increased in the young generation [1]. Recent investigations revealed that a higher prevalence of myopia in children is associated with a higher type of school attended and with more time spent with indoors studying or with less time spent on outdoor activities [2–6]. If the amount of intensive intellectual education with a high amount of indoors studying is a risk factor for the development of myopia, we postulated that the age groups, which were school children at the time of the Great Leap Forward or during the Cultural Revolution, may have a lower prevalence of myopia than the age groups which were older or younger. We therefore analyzed the prevalence of myopia in a population-based study on adult residents of Beijing and compared the refractive error and ocular biometric parameters between age groups. The refractive error as a measure of myopia is strongly associated with the axial length and corneal curvature of the eye. The latter two parameters are measured by biometry. Since the myopic refractive error can increase at older age due to an age-related increase in the refractive power of the lens, we took the axial length and the ratio of axial length to corneal curvature (AL/CR) as surrogates of myopia [7]. Since the AL/CR ratio includes corneal refractive power, AL/CR as compared to axial length as single parameter is a better correlate for refractive error. Axial length and corneal curvature do not show marked age-related changes beyond an age of 30 years. The whole study was divided into two parts. The crosssectional part included all participants of the populationbased Beijing Eye Study 2011 who had undergone biometric measurement of axial length and corneal curvature [8]. The second study part included all participants of the Beijing Eye Study 2011 and all participants of the baseline examination in 2001 (Beijing Eye Study 2001), for whom the refractive error was measured, who had not previously undergone cataract surgery, and whose age fell into the age groups of 56–58 or 59–61 years [8]. The Medical Ethics Committee of the Beijing Tongren Hospital approved the study protocol and all participants gave informed written consent. Out of 4,403 eligible individuals in 2011, 3,468 (78.8 %) subjects participated. All study participants underwent a detailed interview and ophthalmic Y. X. Wang L. Xu (&) J. B. Jonas (&) Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, China e-mail: xlbio1@163.com