If blind folded, I would probably experience tripping overr and, hence, pain, dizziness and death. I was thinking more metaphysically. However, this is interesting. Not too sure how practising techniques blinded would go
Technically I think it is best not to really focus on the uke anyways, especially not their hands, limbs or sword. It distracts me of where and how the person is actually moving I think.
"Do not stare into the eyes of your opponent: he may mesmerize you. Do not fix your gaze on his sword: he may intimidate you. Do not focus on your opponent at all: he may absorb your energy. The essence of training is to bring your opponent completely into your sphere. Then you can stand where you like. "-- O' Sensei