Before I had my first big exacerbation, a bout of optic neuritis in 2006 (and before I had any clue that I had MS) I had a few days where I'd wake up and my vision would be blurred. No pain, just blurry vision that would either go away in a few hours, or it would stick around for a little over a day or two and then go away.

I told my eye doctor about that once, and he told me it was probably whatever lesion it was that was responsible for the ON in 2006 in it's early stages.

Weird thing was, that once, the blurriness was in the other eye and not the eye that ended up getting optic neuritis.

Last summer, I did have a month or so of dim vision in the eye that had had ON, but I also had some dimness in the other eye, so whatever is causing my near yearly vision problems must be close to the nerve for the other eye.