Thanks for your replies, everyone.
Continuing the "jg18's vision went down the tubes" saga (
previous post)...
TLDR: There's still no improvement. The doc at UCSF doesn't know what the cause is, let alone when or even if it will get better.
There are still some test results pending and possibly even treatments worth trying in the absence of a diagnosis, but I get the sense we're running out of ideas.

There are some good signs,though, such as normal eyes (other than pre-existing nearsightedness etc.) and especially the normal brain MRI scan, since MRI is an extremely sensitive test.
Still, the numbers are not encouraging: when my vision was tested a few weeks ago with my glasses on, it was around 20/40 in the left eye and 20/70 in the right. When it was tested again this past week, it had dropped to 20/400 and 20/630, again with my glasses on. Not a good trend.
I can still use a computer (obviously) and even a smartphone, although very slowly using heavy magnification. I could probably even read books/magazines with a powerful magnifying glass that included a light, although it would also of course be slow.
But coding while in this state just isn't feasible. I told my boss a couple days ago that I couldn't work, so I'm now on unpaid medical leave. He's understanding and has said that I'll still have a job when (if?) I come back, so that's reassuring. It doesn't hurt that my benefits even include disability insurance.
Speaking of which, now that I've had this for several weeks, it feels less like a short-term medical problem and more like a long-term disability. I can still function except for being unable to work (kind of a problem

), although many signs, labels, and screens are more or less illegible. I wonder if this is how it feels to be illiterate. EDIT: On top of that, most movies and TV shows are pretty much unintelligible, and almost all games are unplayable.
The only day-to-day thing that's really scary is crossing intersections. I usually can't tell whether the sign says walk or don't walk, even the sign on my side. If there's no pedestrian/motorist traffic around to help, then it's kind of a roll of a dice.

That's only happened once or twice, but still. It's easier to see the light at night, but it's also easy to confuse it with the other light sources around it.
It's entirely possible that one day soon I'll wake up and it'll be better or at least mostly better. It's also possible although maybe less likely that I'll wake up and it'll be much worse, maybe even near-blindness. Incremental changes are much harder to tell, although I did have the sense in early January that it was getting worse, as much as my parents wanted me to tell them it was getting better.
I try not to let it all get to me, but of course it does sometimes. If it doesn't get better, that would end my programming career. I will say that if/when it does get better, I'll never think of people with disabilities the same way again.