Maybe you have a binocular vision disorder and need vision therapy?

Simon,

Depends on age, most people over 50 while have a couple of UBOs:
Unidentified Bright Objects on an MRI: typically perceived as a small
infarct. If under 35 and there are a few of those, can't be sure, but it may
suggest a problem. In any event probably an idea to have a follow up done in
the near future.

There might be other ways to detect MS: presence of an ig class in the CFS,
s100B perhaps?. Vision problems are often the first(optic neuritis) to
appear in MS but my understanding is that they can detect "pallor" in the
optic head when this is occurring. There is also pain with optic neuritis.
Have you ever been knocked out or a big blow to the head? Even that can
leave lesions. Don't seem like MS but I'm too far away.

"Filling in" is exactly what seeing is about and one reason why the idea of
the eye as a camera is so terribly misleading. There is some very
interesting research on that. Bloody brains, always playing tricks on us.