The aim of this page is to give a brief introduction to the human visual system, and to briefly explain why we move our eyes and it's relevance to eye tracking.
The human visual field spans about 135 x 220 degrees and is, as previously mentioned, divided into three main regions: the foveal, parafoveal, and peripheral regions. We primarily register visual data through the foveal region which constitutes less than 1% of the visual field. Even though this represents only a small part of our field of vision, the information registered through the foveal region constitutes about 10% of what is sent to the brain through our optic nerve (Essen & Andersson 1995). Our peripheral vision has very poor acuity, and is only good for picking up movements and contrasts. Thus, when we move our eyes to focus on a specific region of an image or object, we are essentially placing the foveal region of the eye on top
Eye movements have 3 main functions which are considered important when we process visual information: