My friend Alex has a really bad bug: we were playing Minecraft hunger games at a.themchgames.com and for some reason, everything block turned black. He could still see the sky, other players, and particles, and now its affect still remains in other servers; however, not in singleplayer. It might've been some potion effect, but it doesn't act normally as Blindness. And yes, he's reinstalled Minecraft a bunch of times. Its a really annoying bug, and if anyone could find an explanation or solution, please tell me ASAP.
EDIT: Its also in his singleplayer worlds now.
https://www.youtube.com/user/knifebladepresents
try this video, might help
https://www.youtube.com/user/knifebladepresents