Hi Calyx, one of my cats has been blind for about 4 or 5 years now. If Calyx has high blood pressure, it's a pretty good bet that it caused retinal detachment, which led to his blindness. That's what happened to my Margaux. Unfortunately, the chances that a cat who's already blind to that point will regain his eyesight are pretty small. My vet said Margaux may have a little peripheral vision, but that's it. She has some light perception; space I'm not so sure about.
Calyx has probably memorized the locations and distances in your house if he's not having trouble finding his food/water/litter. Obviously, it's important to not move furniture. If I come in and put groceries or packages on the floor, I make noise so that she knows that there's something taking up what's usually empty space. I have hardwood floors and a short set of stairs to the front door, and Margaux used to fall down the stairs every now and then. I'd just hear "thump thump".
I got those little carpet strips that you can put on each step, and I put one at the top of the stairs too, so that she'd know when she came to the edge.
I leave the hallway light on at night and sometimes during the day too if I know I'm going to be home late.
Sometimes, her distance judgment is off by a couple of inches, and she'll just bump into everything. I've taken to saying "be careful! be careful!" when she's about to walk into something. It's taken a while, but she now understands that this is a warning, and she'll slow down or stop and then proceed with caution.
I'm assuming that your vet put him on meds? My cats (both are hypertensive; only one is blind) are both taking Norvasc. The blind one was on the generic for Norvasc, and it didn't seem to be doing anything for her blood pressure, let alone her sight. When I moved and got a new vet, she told me that Norvasc was one of the meds for which many people found the generic completely ineffective. It's expensive though. The blood pressure is normal for both now, but I don't think Margaux's sight has really improved. Maybe just a tiny bit, because sometimes she seems to react to motion. But she can't see things that are right in front of her. Hence, the sad little bumps that I hear every now and then.
I don't have a fountain, so I can't suggest anything there. I'll bet he'll find the stream on his own with a little exploration though. You might try tapping something where the stream is so he can follow his ears.
I can't think of anything else at the moment, other than to give lots of love and attention. Margaux was never a lap cat, but since she went blind, she's become much clingier and seems to want more affection - maybe to feel more secure.
I feel very bad for her sometimes, and sometimes terribly guilty for not realizing what was going on until she was already nearly totally blind. But other than a weird ailment that she's had recently, she seems generally happy and still even plays. She can't really chase, but if I wave a wand toy, especially one that has a bell on it, in front of her, she senses the motion and will try to grab it. She seems to have adapted well - maybe better than I have!