1. A system for monitoring movement of a person's eye, comprising: a device configured to be worn on a person's head; a light source for directing light towards an eye of the person when the device is worn; a camera on the device for monitoring movement of the eye, the camera configured for generating video signals representing video images acquired by the camera of the eye; a processor communicating with the camera for processing the video signals to analyze a pupil of the eye by identifying the pupil of the eye from the video signals and monitoring at least one of a size of the pupil and an eccentricity of the pupil; the processor is further configured for correlating the video signals to determine the person's physical or mental state based at least partially upon analysis of the pupil identified by the processor; and a display coupled to the processor for displaying video images of the eye from the video signals processed by the processor, the display superimposing a graphic onto the video images to identify the pupil.