As far as I can tell, Toph needing to touch the ground directly is probably more spiritual need than physical. She's using the vibrations in the ground to "see", but it's not a physical thing. She's using her earthbending to both sense and interpret those vibrations as something she can "see". Without her Earthbending, she's be like any other blind person.
I recall that there was a moment in the cartoon when she tore out the bottom of a pair of shoes in order to have a better connection of the earth. I think she was rather relieved when she did this, though it's been a while since I watched A:TLA. Considering the technology level, Toph wouldn't get anywhere near as much disruption in her senses as Taylor would today, so I think it's more of a need to be directly touching the earth to better use her Earthbending to sense and interpret the signals she's getting.
I recall that there was a moment in the cartoon when she tore out the bottom of a pair of shoes in order to have a better connection of the earth. I think she was rather relieved when she did this, though it's been a while since I watched A:TLA. Considering the technology level, Toph wouldn't get anywhere near as much disruption in her senses as Taylor would today, so I think it's more of a need to be directly touching the earth to better use her Earthbending to sense and interpret the signals she's getting.