Aside from the effect it may have on a child's eyes, I've noticed in the case of my child too much time spent staring at a tv screen results in

-worse behavior in general
-lowered attention span (his attention span is already very short to begin with)
-lack of motivation to do anything other than stare at a tv or an iPad
-poorer performance in school

I often wonder if increased electronics use by children at a very young age is related to the huge increase in cases of attention deficit disorder (ADD) and attention deficit hyperactive disorder (ADHD) in the United States.