I don't have the persistent visual snow. Instead I have the transitory kind. Once sunlight in my eyes caused it; the first time. Lately watching football games on the big screen TV where there's stuff scrolling at the bottom and top of the screen while the game is playing have caused it. I think my brain tries to watch everything showing on the screen at once and it can't handle it; then it spaces out. I get moving pixels in one part of my vision but it really adversely affects my entire vision.
Fortunately, I have been prescribed 10mg Propanolol for heart rhythm problems as I have Wolf-Parkinson-White. I usually only take a pill if I'm having rhythm problems. However, if I take a pill when the visual snow starts the snow goes away in about 30-45 minutes after taking the Propanolol. I'm passing this along in case it might help others facing this problem. I first had this about 4 or 5 years ago and when I looked on-line then I didn't find much info. I had this problem again today and found this forum so I decided I would post. Luckily I only have these every 8 to 12 twelve months apart and have only had a few.