This is a neurological issue that is one of the features of AD/HD, but could also be a feature of any number of other neurological challenges.  A child who has pdd-nos, a child with OCD, cerebral palsy, and a number of other conditions may have eyes that are unstable.  In addition to the pons and midbrain level traumas or developmental gaps that might produce visual instability, there can also be a viral component.  I am working with a family who is also working with Dr. Klinghardt and whenever the retro-viral load in the system goes down through treatment the tics, including visual-motor small and rapid movements, called saccades, are significantly reduced or disappear.

As for the interesting differences between children,we want to remember  that ‘each brain is a universe unto itself”.   You can’t see dysfunction in a child and predict the neurodevelopmental challenges that you will see in testing.  And you cannot assume from functional neurodevelopmental testing what the diagnosis would be unless you have seen the child him/her self.