Most common vision problems can be treated if they're caught early. But a few years can make a big difference in the severity of the problems.
And for many pediatric eye doctors, it's a race against the clock to prevent blindness. After a certain period of time, after ages 6,7 and 8, the problems can become a permanent loss that's irreversible due to absolute changes in the brain. And vision problems in kids aren't always obvious.
Parents should look for signs like children holding a book close to their face while they're reading, or only being able to use one eye to see certain things.