S4 is known to cause some vision sides, i avoid it too. although they do go away after you stop it and if lower dose it is minimal, but still.. personally not a fan of that oneBuddy of mine complained of night blindness with S4 I believe? Messing with vision can not be a good thing and has kept my clear of those. Not enough research for me at this point. Just my 2 cents. We got some professionals here who if take advice over mine!!