1) This isn't normal? I get this plus an auditory analogue (imagine an impossibly high pitched sound like crickets chirping) which I've always figured was just what my 'noise floor' sounded like.

2) Why would you see this as something to cure? (Edit: Assuming it's something you only see at very low light levels - if you get it all the time even in bright light then that would be pretty bad.) It's just what you get when your visual system's auto-gain tries to amplify darkness. I'm not sure what else you'd expect.

Couple of personal observations:

- Most of the time I only notice snow or artifacts if I'm consciously looking for them or don't have anything else conscious occupying the brain (e.g. staring at a wall out of boredom, or closing my eyes and still paying attention to visual input)

- Once you start looking for visual artifacts, you'll see them everywhere. Right now if I stare at my ceiling in dim lighting, I see little multicolored 'heat wave' patterns roiling about as my visual sensory system works overdrive to extract more signal that there actually is. I also notice a slight 'ringing' halo around bright objects. But as soon as I try to do anything at all, my brain apparently decides that other things are more important and actively filters all this stuff out

Don't discount the possibility that you're putting yourself in a vicious cycle here:

perception of something wrong -> heightened subconscious threat processing (your brain starts looking for a problem in your visual perception) -> more conscious awareness of visual artifacts -> perception of something wrong

The way to break that cycle is to just worry about more important matters, and it'll either go away by itself or you'll stop caring.

This is tinnitus, something I've suffered from since childhood and it has gotten worse recently after attending a concert and standing too close to the speakers. It does indeed feel like a "noise floor"; in a silent room it becomes overbearing.

Please refer to my comment here. https://news.ycombinator.com/item?id=15681108