A teacher guides students to do eye exercises at a middle school in Hengshui, north China's Hebei Province, Sept. 1, 2018. To cultivate a good habit of using eyes, schools in China prepare eye-care activities for students on the school opening day which falls on Sept. 1. (Xinhua/Zhu Xudong)

Students participate in an activity while wearing eyeshades at a middle school in Hengshui, north China's Hebei Province, Sept. 1, 2018. To cultivate a good habit of using eyes, schools in China prepare eye-care activities for students on the school opening day which falls on Sept. 1. (Xinhua/Zhu Xudong)

Medical staff illustrates eye care tips at a middle school in Hengshui, north China's Hebei Province, Sept. 1, 2018. To cultivate a good habit of using eyes, schools in China prepare eye-care activities for students on the school opening day which falls on Sept. 1. (Xinhua/Zhu Xudong)

Pupils do eye exercises at an elementary school in Xingtai City, north China's Hebei Province, Sept. 1, 2018. To cultivate a good habit of using eyes, schools in China prepare eye-care activities for students on the school opening day which falls on Sept. 1. (Xinhua/Mu Yu)

Medical staff illustrates eye health knowledge at an elementary school in Xingtai City, north China's Hebei Province, Sept. 1, 2018. To cultivate a good habit of using eyes, schools in China prepare eye-care activities for students on the school opening day which falls on Sept. 1. (Xinhua/Mu Yu)