Hyperopic amblyopia is due to under-use of that eye due to non wearing of glasses. That is the reason why we recommend regular eye check ups of all children at the age of 3 yrs.
Now he has to wear prescribed glasses regularly. Please find out from the doctor if the fixation is foveal or extrafoveal. If it is foveal, some exercises can improve the quality of vision to some extent. You could also consider CAM vision stimulator.