Well, a widely accepted canonical authority would seem to be "why" right? :-)
As far as explanations: Apostolic Canon 78 (listed immediately after) says that the deaf or blind may not be made a bishop "...that the affairs of the Church may not be hindered".
Unfortunately the Nicene and Post-Nicene Fathers reference that I have does not have any additional commentary. I can say that I know of at least one priest who very nearly was ruled canonically ineligible at his ordination because he has a tremor in his hand. The idea is that you cannot ordain someone who might, through some physical infirmity, mishandle the Holy Gifts. Thus the reasoning "...that the affairs of the Church may not be hindered".
Musing on this for a few minutes, I might add that such an infirmity might also preclude the presbyter or bishop from "working the Lord's vineyard" so to speak. The shepherd has to tend his flock.