More students wear glasses - that was the first thing fourth-grade teacher Qu Tingting noticed when she entered the classroom at the beginning of the new semester at Tairi School in Shanghai's Fengxian district a month ago.

The 9-year-old students have few school homework assignments, Qu said, and almost all of them play games on tablet computers every day.

"Digital gadgets aren't allowed during the breaks between classes, but almost all of the children's parents told me their kids use iPads after school," Qu said.

As more children succumb to iPad-mania, eye doctors remind parents that the gadgets may impair youths' eye development and raise the probability of shortsightedness.

Eye tests revealed that fourth-grade Tairi School students' eyesight declined slightly on average since last semester, according to the head of the school clinic, surnamed Lu.

Qu said eight of the 40 children in her class now wear glasses. There were only four before the Spring Festival holiday in February.

Zhang Rongfang, a retiree in Shanghai, said her 5-year-old grandson is obsessed with playing iPad games. The boy is unwilling to stop even when the family dines together in a restaurant.

"Everyone in the family says the boy is very smart when they see his little fingers darting here and there across the screen, but they don't know that he spends hours playing the games at home every day," Zhang said.

The boy's parents divorced last year and he lives with his grandparents. To keep him from feeling lonely, his father bought him an iPad last summer. He has been fascinated with the "almighty game player" ever since, Zhang said.

Zhang was unaware of the damage tablet computers could do to the kindergartner's eyes until he continuously complained about eye pain recently.

A micro blog post about a 4-year-old becoming nearsighted from playing too much with his iPad stirred an online sensation recently - it has been forwarded more than 26,000 times.

"Kids are fascinated with playing games, reading fairytales and watching cartoons on iPads, but their eyes have become victims of the 'poison Apple'", read a micro blog post updated by "weiboyougui2011" on March 5.

Eye specialists warn parents to keep children from constantly playing with electronic products.

IPads shine with bright colors, which is a strong visual stimulus, said Tang Dongrun, head of the ophthalmology department at Tianjin First Central Hospital.

"The muscle that adjusts the pupil remains highly tensed to adapt to changes of light. And the flicker of the electronic screen intensifies the frequent movements of the muscle," Tang said.

Moreover, children are more susceptible to eye injuries because to their optical system is still developing, Tang said.

You may contact the writer at zhouwenting@chinadaily.com.cn