Teens and preteens who complain of sore eyes during homework or get headaches while reading may have convergence insufficiency (CI), which makes eye muscles work harder to focus up-close. In healthy eyes, to bring print into focus, both eyes must turn slightly inward, or converge, but kids with the problem have eyes that don't turn together properly to read.
As many as one of every 20 students may have some degree of this condition, which is often missed during exams. Young children may not complain as much as teens and preteens, whose homework requires more reading.
CI is treatable, most commonly with eye training performed in a doctor's office for 3 - 4 months. If your kids complain that their eyes hurt, check with your doctor.