I think ,he is doing pretty well if he is able to drive also ..
Treqtment will only be supportive as in supplements and physiotherapy only ..
You have to ignore it ,and over period of time , will get adjusted ..
As in primary gaze, there is no diplopia ..dont think prism also will be needed
Next Steps
can take opinion with Neuro Ophthalmologist
Health Tips
control BP ,
sugar , take vitamins n be active