It is hard to know exactly what we see because our brain processes it so much and then we have to put it into words and we could easily be describing different experiences the same way or same experiences differently.

I would guess any light receptor produces noise whether that is a few stray protons or just thermal chemical/electrical processes. I would think for most people the brain is receiving noise very much like this but how they experience it depends on how it is processed. Unless there is some after image from recently staring at something bright, when my eyes are shut my brain gives me an impression of nothing which is almost certainly not what my retina is detecting.