A study done in 2009 showed that the number of people with nearsightedness has been increasing over the last 30 years, but whether this is due to the amount of time we all spend doing "near work" is unclear.
The most important thing you can do is to limit your child's screen time, counting the time they spend on the phone texting, on the computer, or in front of the TV. The effect is cumulative. Encourage your child to take a break from the screen every 20 to 30 minutes to let their eyes rest and to adjust to some distant vision.
Smaller screens with smaller print also require more work for the eye muscles, which must contract to allow the eyes to focus. So, having your child read articles and lengthy papers on a bigger screen would be preferable to long reading tasks on a smartphone.
I see a lot of kids with tired necks and backs from leaning over their computers. They rarely associate their "screen time posture" with other aches and pains. Kids should be encouraged to sit up in a chair at a desk with their feet on the floor while working on a computer.
A computer or game screen should be at least 20 to 28 inches away from a child's eyes. Have your child move around and change positions when possible while playing games, etc., away from a desk.
Lastly, and most importantly, limit your child's total screen time to no more than 2 hours per day. That may be more challenging than seeing the screen!
DR. SUE HUBBARD is a nationally known pediatrician and co-host of "The Kid's Doctor" radio show. Submit questions at http://www.kidsdr.com.