1. A non-transitory, tangible, computer-readable storage medium containing a program of instructions that cause a computer system running the program of instructions to display an incoming image on a head-mounted display with a perimeter portion of the image being occluded on the display by the program of instructions; and one or more of the following: detect, using a sensor configured to monitor a user state in response to viewing the image, the user state, and dynamically throttle the amount of the occlusion in response to the user state being in an abnormal physiological state or an expected abnormal physiological state; wherein the amount of the occlusion is manipulated by rendering the occluded portion to a textured polygon and manipulating the textured polygon; wherein the amount of occlusion is based on one or more measurable parameters that include a virtual environment content, a system parameter, or a system performance; wherein the amount of occlusion is based on an amount of elapsed time; wherein the amount of occlusion is based on a user's previous virtual environment experience; or wherein the amount of occlusion is based on influencing a user's experience with the virtual environment, influencing a task performance of the user, or completed tasks within the virtual environment.