Binocular vision is the visual perception of objects with two eyes.
The fundamental difference between seeing with one and with two eyes is in the appreciation of the depth of the subject. When an object is looked at through two eyes, each eye sees a little more than the other of its own side of the object. In addition each eye sees the object against a different part of the background. The first difference increases as the object comes closer to the eye, the second increases as it gets farther away from the background. When the separate pictures seen by the two eyes are fused into a single impression in the brain, these effects combine to give an impression of the depth of the subject and its position in space between the observer and the background- i.e., a stereoscopic picture.
The stereoscopic effect of binocular vision grows less as the subjects get farther away- i.e., as the separation of the eyes becomes less and less in proportion to the distance of the subjects. After a certain point is reached, both eyes see substantially the same picture and the sensation of depth is no longer apparent. For a scene viewed at a given distance, the stereoscopic effect is greater the more the scene extends in depth.