Myopia development and progression has become a public health problem in recent years due to increasing prevalence across the world. It is estimated that myopia will affect approximately 50% of the world population by 2050[1]. It is a multifactorial refractive disorder. Both genetic and environmental factors play a role in the etiology. Studies showed that there is a regional difference in the prevalence and the prevalence rate is two times higher in East Asia [2]. Intensive education systems have changed the children's environmental and social factors and considered as an important reason for this regional difference. Increased near work activities and decreased outdoor activities pretended to be leading predisposing factors for the development and progression of myopia. However, the results of the previous studies were controversial [3], [4], [5], [6], [7].

Myopia presents a faster and longer progressive pattern in childhood, and progression can lead to degenerative ocular complications [8], [9]. It is important to understand the underlying mechanisms to prevent the progression and related complications of myopia. Questionnaires have been used in previous studies for evaluating near-work and outdoor activities in children [3], [10]. Some interventional studies have concluded additional outdoor activities slows onset and progression of myopia [11]. However, the exact mechanism responsible for the protective effect of outdoor activities on myopia progression is not clear yet. Exposure to brighter light, ultraviolet light, levels of vitamin D, therapeutic effects of outdoor environment and dopamine levels suggested as the protective factors [12], [13], [14], [15], [16], [17].

Wearable sensors, which evaluate light exposure and near-work activities, are relatively new. Various devices and device locations have been used for better understanding light exposure levels. It is concluded that wrist-worn devices do not show the illumination level of the eye, and clothes with long sleeves could affect the light sensor. Comparison between a wrist-worn device and photometer showed that Actiwatch 2 have been reported approximately 46% of the true light exposure under ∼30,000 lux sunlight [18]. The Actiwatch 2 has been compared to a spectacle mounted device and a photometer. Both Aciwatch 2 and Clouclip devices have been underestimate light exposure compared to the photometer, and the incompatibility was greater for Actiwatch 2 [19]. Illumination levels more than 1000 lux have been used as a threshold for outdoor activities in previous studies.

The aim of this study is to evaluate the percentages of near activities, as well as the percentages of photopic, high mesopic and dark illumination conditions in progressive myopic children objectively, thus, understanding and preventing the behavior that may lead to progression in patients with myopia.