Notebooks, writing tools and laptops are standard supplies on a parent’s back-to-school shopping list. But one important appointment that can easily be overlooked in the back-to-school frenzy is a child’s eye exam.

It’s estimated that one in four school-age children faces difficulty with reading and learning because of undiagnosed eyesight disorders. Some schools may offer onsite testing, but optometrist Dr. Jennifer Wademan said a comprehensive exam at a doctor’s office can pinpoint overall eye health and how the eyes are working and “teaming” together.

Wademan said a child’s inability to see correctly can mean low performance in the classroom.

“Eighty percent of learning is visual,” she said. “The concern that comes into play as kids approach back-to-school time and they’re in the classroom is if our children aren’t seeing clearly in the classroom, or their eyes are not working well together, we worry about the impact on their academic performance.”

Riley Hospital for Children in Indianapolis said amblyopia, or “lazy eye,” is the leading cause of vision loss in children. If left untreated, the condition can continue into adulthood.

Wademan said squinting is often an indication of vision challenges. Other signs are if a child is overly tired or has frequent headaches. She noted these are all symptoms parents often miss or don’t associate with vision problems.

“Other signs may be that your child’s avoiding certain activities, like reading. Perhaps they’re excessively rubbing their eyes,” she said. “Watch your child. Are they tilting their head or turning their head in a manner in order to see something?”

She added the good news is that most vision problems are treatable. Although children get additional screen time after school for socializing on their favorite apps, adults should also protect their eyes against dryness, irritation and redness. Wademan recommends the 20/20 rule: For every 20 minutes of screen time, take 20 seconds and look at least 20 feet away.