Diving after removal of acoustic neuroma

 I have a 40 year old who had an acoustic neuroma removed 7 years ago. He is completely deaf in that ear. He has no symptoms arising from his vestibular apparatus. There are no signs of problems with his balance, no nystagmus, and he passes a Sharpened Rhombergs on the 3rd attempt. His good ear has perfect hearing and good Eustacian function. He is going back to see his ENT surgeon for a review and then will return to me to discuss his fitness to dive. He is very keen to dive and may accept putting his hearing at some risk if he does dive. However, I would value any input that I can use when he returns to see me.