Physical and Physiological Bases of the Visual Field
When an eye fixates on any object in the space, it can not only see clearly the object but also can see objects in a certain space around the fixation point. The summation of the space one eye can see is called the visual field (VF) of this eye. It needs to be noted here that only the space perceived or seen by the tested eye, when it stares at or fixates on the object without any movement, can be called as visual field. Such scale is determined by the distance between the fixating eye and fixation object and the size of the object in the space. Meanwhile, the real visual field, as mentioned above, is a three-dimensional concept, which contains not only the spatial extent that can be perceived around the fixation point but also the visual sensitivities at different positions in the space.