I get both of these, the very short bursts of rapid nystagmus (my poor Siamese kitty has this too, but hers is much slower! lol) usually occurs when I’m either very tired, on the verge of an intense migraine, or WAY past my level of stimulants.. I take 70mg of Vyvanse daily and thanks to my brain fog have definitely taken a double dose on multiple occasions! (I believe that this is also a common occurrence for abusers of stimulant drugs, so I wonder if there is a correlation between dysautonomia, a flooding of adrenaline and bouts of nystagmus?)
I have also had visual snow as long as I can remember, in exactly the same way as Maffin mentioned.. I also have photophobia and it is much more noticeable after flashes of bright light or staring at a computer screen before bed. (I remember watching the tiny red dots as a kid and trying to make them fly across the room when trying to fall asleep at night.. lol)
I always assumed these were normal things, I’m starting to realize just how abnormal I might have been, haha 🙂