When the eye looks at a specific point or object, that point is seen clearly. Other objects within a large area away from this fixation point can also be seen, but less clearly. The area that can be seen around the fixation point, without moving the eye, is known as the field of vision. The extent of the field is limited inwards by the nose, above by the brow and below by the cheek. The visual field thus has its greatest extent outwards from the side of the head. The field of vision of each eye overlaps to a large extent so that objects in the centre and towards the inner part of each field are viewed by both eyes together. Because the eyes are set slightly apart, each eye sees objects in this overlapping part of the field slightly differently. It is because of this slight difference that objects can be perceived as three-dimensional.

Defects in the visual field (scotomas) can be produced by a variety of disorders. Certain of these produce specific field defects. For example, GLAUCOMA, some types of brain damage and some TOXINS can produce specific defects in the visual field. This type of field defect may be very useful in diagnosing a particular disorder. The blind spot is that part of the visual field corresponding to the optic disc. There are neither rods nor cones on the optic disc and therefore no light perception from this area. The blind spot can be found temporal (i.e. on the outer side) of the fixation point. (See also EYE.)