I still haven’t come across another case of this blurred vision aftereffect, or devised a plausible mechanism. There can be lasting pupil contraction from cluster headache, but I think my pupil is normal.
The return to clear vision happens mostly gradually, so the blurriness isn’t nearly as great as a few days ago. Also it is just in my left eye, so I can do some things by looking with just my right eye.
Occasionally I end up with it in both eyes, though not equally badly.