Stereoscopic Vision

"Stereoscopic vision" (steropsis) is vision that involves perception of distance and depth as well as the height and width of objects. Such vision is largely due to the amount of distance between the pupils of the eyes. Objects that are closer (less than twenty feet away) produce slightly different retinal images. That is, the right eye sees a little more of one side of an object, while the left eye sees a little more of the other side. These two images are somehow superimposed and interpreted by the visual cortex of the brain, and the result is the perception of a single object in three dimensions.