This is called nystagmus, which is usually caused due to poor vision for any reason since childhood. His vision would definitely be affected and must get him seen by a good eye specialist or eye hospital to find the reason for it. The eye specialist would need to examine his eyes after dilating the pupils. Unfortunately, not much can be done now to reduce this nystagmus, but steps should be taken so that his learning and education do not suffer. Sometimes there may be albinism or neurological cause, which will need investigation accordingly.