Of course, visual snow cannot lead to blindness, so you do not need to worry about it. For the causes, you should know that chemical changes can just lead to visual snow. Of course, because of visual snow, some visual problems, such as starbursts, increased afterimages, floaters, trails can be possible. But there is no evidence which have shown that it can lead to blindness. By the way, blindness is often related with retinal detachment. So just be careful about it.
First of all, you should go to the ophthalmology to take an eye examintation to see if there is any abnormity on your fundus or not. If there is not any abnormity on your fundus, then you can rest assured. Visual snow can be temporary for some days, or sometimes can last for a long time. To some extent, it depends on the indivisual health condition, personal immunity and state of mind for people to get rid of the visual snow. You had better keep a good mood, and do not be too anxious or nervous. Take adequate rest everyday and do not overuse your eyes. It is very rare that visual snow could lead to blindness. Nowadays there still are not exact causes for visual reasons, but you can try clonazepam, which is a preferred medicine for people with visual snow.