Doctors used to see vision problems related to computer use primarily in adults who spent long hours working at a computer. 

But these days, it's not just adults logging serious screen time. Experts say even elementary school students spend hours on computers, smart phones and iPads, and it's having an effect on their eyes.

"Some research shows that about 90 percent of people that use a computer three hours or more a day experience some sort of eye or vision condition," said Dr. Geoffrey Goodfellow, of the American Optometric Association.  "So that's not just adults.  That certainly affects our children as well who use these devices at home as well as in the classroom."

According to a new survey by the American Optometric Association, 60% of children spend up to four hours a day looking at a computer or digital device.   For older kids, the numbers are even higher.

The result can be a condition known as computer vision syndrome.

"Computer vision syndrome or CVS is a collection of symptoms that go along with using laptops, computers, smart phones, iPads, all of these devices for many hours a day," said Goodfellow.

Symptoms can include eye strain, headaches, fatigue, burning or tired eyes and blurred vision.

Experts said you can't rely on children to let you know there's an issue.

"Children don't do a very good job of letting us know about eye and vision problems because they kind of assume that everybody must see that way.  But a lot of times you can notice children that kind of furrow their brow or will rub their eyes or will cover an eye while reading or doing other behaviors that may clue you in, even if they're not complaining of a problem that one exists," said Goodfellow.

The solution is something called the "20-20-20 Rule." Experts said for every 20 minutes that you're using one of these devices, take a 20 second break and look at something 20 feet away.

"That's also something for educators and teachers to be mindful of as well," said Goodfellow. "As they structure the day in the classroom, to make sure that every 20 minutes or so, they change gears and draw children's attention to either the board or something else in the classroom that will give their eyes just a 20 second break before they return back to their computers again."

Experts said getting an annual eye exam, positioning devices to reduce glare and encouraging children to blink more can also help reduce the risk.

"When we use these devices, we don't blink as much, and that can cause your eyes to dry out or be irritated," said Goodfellow. 

"Most of the time these computers and devices aren't really causing any long term damage to the eyes, but they're really uncovering these small eye and vision problems that are undetected in the first place."

To learn more about computer vision syndrome, click here.

To find out more about computer vision syndrome in children, click here.