What could cause blindness in a wild animal?

He could have been sprayed by some animal in the eyes. I know that spitting cobra venom causes blindness. Also, he could form some disease, maybe cateracts or something, but I'm not sure how it is caused. Also, another animal could have injured it. I know that many animals are injured by each other for territory. Or male lions ofter try to kill the young of other male lions, to prevent future opponents.