Systems and methods are provided that allow a person to exert control in real space as well as in virtual spaces. Eye tracking is employed to determine the direction of the viewer's gaze, and head tracking can be used as needed to track the viewer's head in order to provide a stable virtual environment. Eye vergence can then be used to as a triggering mechanism to initiate responses stored in association with objects in the field of view. Additionally, eye vergence can be used to provide a continuous control.