During a stressful military battle, fong suddenly went blind. when hypnotized by an army psychiatrist, his blindness vanished. fong apparently suffered from a:

I believe the answer is: Conversion disorder

Conversion disorder is characterized by unexplainable physical condition such as Blindness or paralysis.

It is caused by the damage in nervous system that could be created when the patient is over exposed to stressful stimulus (such as military battle)