Daf Yomi - Yoma 53 - Walking Backwards when the Rebbe is Blind

Rashi states that Rav Yosef was blind. The Sfas Emes comments that it would seem from here that there is an obligation to walk backwards away from your Rebbe even if he cannot see you. He points out that from a Gemora previously, it is evident that this would not be the case. The Gemora states that one should walk backwards until the Rebbe can't see him anymore. This proves that if the Rebbe is blind, one doesn't have to walk backwards at all.

It would seem to me that there can be a distinction. There is always an obligation to walk backwards as the student must respect his Rebbe and that is regardless if the Rebbe can see him or not. However, the requirement is only until you are out of sight. If the Rebbe is blind, the talmid should walk backwards for a moment to fulfill his obligation and then he can walk regularly. (This is just a sevara, not halacha.)