Well, in my opinion, long time of computer use cannot lead to visual snow, so you do not need to worry about it. But on the other hand, if you watch computer for too long time, it will just increase your eye pressure. In that way, it will lead to eye strain. In a long term, it will just affect your vision. So just be careful about it. By the way, visual snow is a transitory or persisting visual symptom where people see snow or television-like static in parts or the whole of their visual fields, especially against dark backgrounds. And because of that, it will just make your eyes uncomfortable. And, chemical changes can just lead to visual snow.