I did volunteer work for Cats Protection a few years back, answering the phones for my area. A man called - he'd found a black cat, who appeared to be blind, wandering along the side of a busy main road, bedraggled, and very thin. Usually I'd ask one of the other volunteers to pick the cat up, but they were busy, and besides that, all the foster places were full. So I asked the chap to bring said cat to me. Not the usual thing, but he couldn't keep him.
The cat, a boy, came to me. He was blind, and also extremely frightened and defensive. I got a litter tray set up, and blocked off a bit of my sitting room, so he couldn't wander, and maybe felt a bit safer. Popped him in the tray, and hoped he'd find his way back there for his toilet. I was amazed he did. Stepped in there, dug around a little, stooped too near the edge.... and promptly shat explosive diarrhoea all over the carpet, and furniture within at least a four feet radius!
Bless him, he even tried to dig over and cover it up. It was a bit of a trying time! Lol.
He really did amaze me though - it was a few weeks before he was found a home. In that time he learned to navigate the whole of my large flat, chase MY cat around when she'd been teasing him, and even learned to climb her cat tree, and get back down. He definitely was blind, but you'd not notice unless you watched him carefully. I have never forgotten that first couple of very shitty days though!