White face border collie, so many different opinions!?

I am just curious if anyone has ever seen what they know for sure is a purebred border collie, with a white face, or partial white face that is deaf or blind? I just got a border collie with a white face, black nose, black pigment around brown eyes, black on one ear and black spotting coming in more and more on the other. I am very familiar with the problems in Aussies and the fact that you should never breed a merle with a merle. This is a black/white BC however, from a breeder who does not breed merles what so ever. I met both parents who have typical border collie markings, a black tri and a black/white. I have seen another of her dogs, almost all white with some speckling who is an adult and not blind or deaf. I did a lot of research before getting the pup and it all indicated that this is not a problem with non-merle BCs...I still feel confident in this but i'm just curious if anyone has actually had experience with a purebred non-merle BC having this "lethal white?"