--Take frequent breaks. Children frequently get so absorbed in what they're doing that they don't notice symptoms of eye strain. Remind them to take breaks. The American Optometric Association recommends the 20/20/20 rule: look away from the screen every 20 minutes, focus on an object at least 20 feet away, for at least 20 seconds. In addition, children should walk away from the screen for at least 10 minutes every hour. A simple timer can help your child remember, and there are even software programs can help by turning off the screen in regular intervals.
What is it like not to be able to see?
Clicking the link above will take you to an article on the CDC website about what it is like not to be able to see.
Give Your Child's Eyes a Screen-Time Break: Here's Why
clicking the link above will take you to article that will explain why it is important to give your child's eyes a screentime break.