Can ick cause blindness (goldfish)?

So yesterday I notuced that one of my fishie friends went belly-up. While removing him from the tank, I noticed my oldest (and favorite) fish had developed a severe case of ick. He was lying on the bottom of the tank, barely moving his gills. I then noted that a few other fish has a few little spots of ick as well, so I treated the whole tank (there are 5 or 6 goldfish and 2 small catfish). Well, he still ha a haze over his eyes, although tge rest of the ick has cleared after two treatments and a 25% water change. When I fed them, I noticed that he didn't eat, although it seems he tried. Has this bout of ick caused my little friend to go blind?! If it did, what are his chances of survival? Would I maybe be better off ending his suffering if he's blind? I don't want the poor thing to starve to death.