BEIJING, Aug. 18 (Xinhua) -- Nearly 90 percent of Chinese parents said their children have an irregular sleep schedule during the summer vacation, while 52.6 percent said the unhealthy lifestyle has weakened the eyesight, according to a recent survey.

Of the 1,989 surveyed parents, 36.1 percent said their children stay up late and get up late during the holiday, according to the survey released by China Youth Daily.

Zhang Qijun, a father of a boy in the fifth grade, said his son often plays video games day and night on mobile phones during the summer holiday, and excessive screen time has disrupted sleep cycles and caused eye strain.

According to the survey, 93.9 percent of the parents interviewed said they were more worried about their children's eyesight during the summer break than usual, as such problems as eye fatigue, irritation and dryness tend to occur in children after spending more hours on digital screens.

Parents and teachers should play their part in supervising the children's proper use of eyes, and help them develop and increase their self-control to resist temptations, said Tang Zhisong, a professor at Southwest University.