For fish, I don't think there's much you can do. The kind thing would be to set him in a quiet corner of the house and care for him until he passes on, so that loud noises and commotion don't scare him. If he seems not to be able to see his food try a smellier, more volatile (frozen foods would work) type of food so that he can sniff and taste his way to it.
I don't think it has affected his sight, as he sees me and eats just fine. No one really comes down here except me and I keep quiet (no loud music or anything like that) and his tank mate is a snail.
But should it get that far I'll do what I can to make him comfortable.