Mathematical modelling of visual perception in two dimensions is described. Although perception is ubiquitously mentioned in literature and it is used in various contexts, its explicit measurable presentation has not yet been given beyond verbal descriptions. In this seminal work the visual perception is explicitly defined for clarity. Based on this definition, it is treated as a mathematical entity in the form of probability in a particular circular region. Theoretically, human vision is expressed in advanced probabilistic terms and the enigmatic relation between vision and perception is mathematically formulated. Here, the perception concerns a special range of interest, coined as vision circle, where percepts describe the vision act of human as the retinal ophthalmic sensing. Perceptual Intelligence Quotient (PIQ) is introduced, that it is subject to measurement. The results of the theoretical considerations are shown to be closely matching the common visual perception experiences as well as the reported visual perception studies, including the variation of peripheral acuity. Two eye-tracking experiments demonstrate that saccadic movement behavior of human is reasonably matching the prediction based on the novel perception theory. The work demystifies the visual perception and understanding its role in sciences. As to the cybernetics, perception plays an important role in the control of complex, integrated processing systems, which are interfaced by indispensable man-machine control systems. In these systems, the role of perception is critical, referring to the hazard situations. The implications of the study are investigated and explained in two such cybernetics applications, too.