I would have a sleep study done on him. You might also want them to do an EEG to rule out any kind of seizure activity.
Sleep walking and talking is not that uncommon in children. Changes in visual depth perception is uncommon. I'd start with an Ophthalmologist. That is the easiest and least expensive. Then a Neurologist. The Neuro would be the best to decide if there is a need for an EEG, Sleep EEG, MRI, etc. The Neuro would be the best to interpret the EEG or sleep study anyhow. You could also see if there is a Neuro-Ophthalmologist.in your area and get both evaluated in one visit.
Bob