How does nighttime light exposure contribute to myopia risk?

Author: Academician Wang Ningli, Professor Li Shiming, Researcher Song Yi Reviewer: [Not provided] Curator: [Not provided] Production Information: Beijing Tongren Hospital, Capital Medical University, Peking University Health Science Center Title: How does nighttime light exposure contribute to myopia risk? Introduction: Myopia is rising globally, especially in East Asia; night-time light exposure may worsen eye development in children. Keywords: ['health', 'vision'] Main text: A study conducted by Academician Wang Ningli and Professor Li Shiming from Beijing Tongren Hospital affiliated with Capital Medical University, in collaboration with Researcher Song Yi from Peking University Health Science Center, has found that light exposure at night (LAN) may promote abnormal eye axial growth through the melanopsin signaling pathway, significantly increasing the risk of myopia in children and adolescents. This finding was recently published in the English version of 'China Science: Life Sciences.'

Myopia has become a significant global public health issue, particularly prevalent in East Asia. Sufficient exposure to daylight and outdoor activities during the day has been shown to have a protective effect against myopia, but the biological mechanisms behind this remain inadequately understood. With the widespread use of artificial lighting, exposure to light at night has noticeably increased, yet its impact on the onset and progression of myopia, as well as the underlying mechanisms, remains unclear. Previous studies suggest that intrinsically photosensitive retinal ganglion cells (ipRGCs), which express melatonin, are involved in the regulation of light signals that control circadian rhythms and eye development. However, systematic mechanistic and population-based evidence is still lacking to determine whether night light exposure disrupts the rhythmic growth of the eyeball through this pathway, contributing to the development of myopia. In terms of mechanism research, the research team first established conditions for nighttime light exposure in a mouse model and found that four weeks of nighttime light exposure (from 21:00 to 23:00) significantly promoted myopic refractive changes, accompanied by an abnormal increase in axial length. Molecular level analysis further revealed that nighttime light exposure significantly downregulated the expression of melanopsin in the retina and interfered with the normal expression of various core circadian rhythm genes. Further exploration using knockout mice lacking the melanopsin gene (Opn4-/-) showed that the absence of Opn4 significantly weakened the myopic effects induced by nighttime light exposure and nighttime blue light, confirming that the melanopsin-mediated signaling pathway is a 'key hub' driving eyeball growth and leading to the occurrence of myopia due to nighttime light exposure. Nighttime light exposure induces myopia in mice, leading to increased axial length, downregulation of retinal Opn4/melanopsin expression, and abnormal expression of core circadian rhythm genes. Knockout of the Opn4 gene suppresses myopia induced by night light exposure in mice and its effect on the expression of retinal circadian clock genes. Based on mechanism research, the team further conducted large-scale population verification. A cross-sectional study included a total of 148,582 primary and secondary school students from 773 schools across 30 provinces in the country. The results indicated a positive correlation between outdoor nighttime light levels in the area where the school is located and the prevalence of myopia. Further individual longitudinal follow-up studies objectively measured nighttime light exposure in children and adolescents and tracked the incidence of myopia over one year. The findings showed that when the average light intensity overnight exceeded 10 lx, the risk of new myopia in children significantly increased. Additionally, if there was weak light exposure during the early stages of sleep, the risk of developing myopia also exhibited an upward trend, with younger children in elementary school being more sensitive to this factor. The longitudinal association between nighttime indoor light exposure and the occurrence and progression of myopia in children and adolescents. This research systematically clarifies that nighttime light exposure is an important environmental factor in the occurrence and development of myopia in children, providing a systematic evidence chain from mechanism discovery to population verification. This achievement not only deepens the understanding of the environmental pathogenic mechanisms of myopia but also offers new ideas and scientific basis for optimizing strategies to prevent and control myopia in children. It highlights the significant value of bidirectional management of light environments in promoting children's visual health.