Hello There are two possibilities A. Dryness B. Refravtive error Start lubricants And consult local ophthalmologist and get his eyesight examined

The most common reason for kids for twitching is either allergy or glasses power. kindly get him checked for this. hope this is helpful

If it's only while watching TV and mobile, its most probably related to screen exposure and it's brightness though it's more common in adults. Try and reduce your child's exposure to these gadgets as much as possible. Make a note as to whether he rubs his eyes more often. Excessing rubbing indiacates allergy which is more common in children during summers.