Is their a trigger to where it changes the players vision to come out as if from a certain units eyes? If so what is it?
That is impossible...
Firstly units have no eyes, they have mesh and meterial to look like eyes but mechanically they are no different than any other surface and mesh on the model. Secondly how can a monocular camera like that which WC3 uses by default support binocular vision like that of most units in the game "appear" to have...
You clearly did not think this through very well...
You can however try moving the camera to a position that appears to be some what like the unit would be seeing if it was real but avoid colliding the camera into models as the result is unrealistic and ugly (yes, all models in computer games are voids of space and often only textured if viewed from the outside).