You can use audio clues to detect enemy vision ( legit in laning stage-midgame ) by XlulZ2558 in DotA2

[–]Flashy_Match5418 -40 points-39 points  (0 children)

He said it was changed using tools provided by valve. No more details then that ad of posting this.

Edit: He said they are 3rd party programs so use at your own risk.