Tehran Times � The Iranian Society of Optometry has warned parents that excessive use of digital screens including iPads and tablets could be harmful to children�s eyes, Mehr reported on Sunday.

Inappropriate use of digital screens leads to health damage for people including kids, the head of the society Ali Mirzajani said.

Parents are worried about using glasses by children but this is not the only problem that may be caused by digital screens, he added.

Extra use of digital screens can even affect the processing of images in the brain, he noted.

�Preschool children can use digital screens for 30 minutes daily. If they use them more than this time, they may face vision problems,� he warned.

Digital screens damage eye muscles and cause dry eye syndrome, he explained.

According to slate.com, some research does, however, suggest that screens could contribute to the onset of problems including near-sightedness and astigmatism. In a study published in November, researchers in Italy recruited 320 3-to-10-year-olds and examined their vision in various ways. They also tracked how long the kids spent in front of screens each day.

They found that kids who spent more than 30 minutes a day playing video games were more likely than other kids to suffer headaches, eyelid tics, double vision, and dizziness. And 90 percent of the frequent video game players had refractive vision problems such as near- or far-sightedness, particularly in their dominant eyes, compared with only half of the less-frequent gamers. When the researchers looked at overall screen use, they found similar patterns: Kids who used screens for more than three hours a day were much more likely to be far-sighted and have astigmatism than kids who used screens less than that.