Yes, we once did a session with the lights off. It was not completeley dark, you still could see your partner dimly. I noticed that it seemed to be a little bit easier for me as I'm used to see only the motion (I'm really shortsightened and sometimes train without my lenses or glasses) where anyone else seemed to concentrate on the little bit they see...... It worked really fine and I enjoyed the session.
We occasionally did it also with closed eyes, but it was much harder, because I had to direct part of my attention on keeping my eyes shut. I also didn't get the timing, but my breathing was all but relaxed. So next time I'll try to relax my breathing and focus on the moment of contact, maybe that'll help.
Hope you'll have more of this interesting training sessions,