I was gonna say nystagmus too.
As for the snow, I have that too. I chalk mine up to my dysautonomia. When it is worse so is the snow. When I’m about to pass out the snow (black snow) gets bigger. My theory for me is based on my symptoms I experienced in my tilt table test where I passed out for first acknowledged time in my life. I had the same snow effect as I left the conscious world.