Visitor's visa interview rules for physically handicapped

[nirva12na]

My parents (who live in hyderabad) would like to apply for their visitor visas to the USA. My father is wheelcahir bound due to a spinal injury.
My question is:
Can physically handicapped applicants be exempt from the personal interview requirement? Can he use the dropbox facility to send in his visa application? And if so, can my parents use the dropbox and apply together or will my mother have to apply seperately since she is physically capable of travelling to Chennai for a personal interview.

[immihelp]

Re: Visitor's visa interview rules for physically handicappe

There is no such rule of being exempt from personal interview because physically handicapped.