In my morning paper.
https://www.thestar.com/news/canada/2016/07/12/deaf-dog-once-thought-untrainable-wins-champion-agility-title.html
I've never weaned myself off from hand-signals, so it never occurred to me what would be difficult about training a deaf dog. Clicker/verbal marker training doesn't work. She said she used a 'thumbs up' hand signal to replace the clicker, which would mean her dog would need to looking at her to have a 'precise moment in time' marked.
Anyway, the article is delightful light reading, Seven is a rescued border collie.