Praise then darkness, and creation unfinished

It's not that I expect voices as a plot point; it's that I'd expect a blind man who had recently been spending a lot of time with his son to at least wonder "Is that you, Edgar?" if they spent long periods alone together. I'd expect, if someone wanted to disguise himself from the king he had spent years as a close advisor to, that the person in disguise would wear a wig. Or course, that would be hard on the audience, who don't know him anywhere as well as the character does. [There are corrective lenses in Lear, as it happens, but they're reading glasses.]