Researchers in South Korea have found that children who overuse smartphones may become cross-eyed.

Researchers from the Chonnam National University Hospital in Seoul examined 12 children between ages seven to 16 who used their phones between four and eight hours a day and held them between eight and 12 inches from their faces, reports the Telegraph.

The result was convergent strabismus, a condition that causes a person's eyes to move inwards until they eventually become cross-eyed.

Fortunately, the condition was reversible in most of the children, who were banned from using their smartphones or tablets for two months. Nine of the 12 children were able to reverse the condition, which researchers claim proves the link between smartphone use and being cross-eyed.

Researchers recommend people avoid looking at a mobile screen for longer than 30 minutes at a time.