binocular vision Humans use numerous visual cues to perceive distance. One of the most accurate of those cues is binocular disparity, which takes advantage of the fact that most people have two eyes.
two eyes = three dimensions (3-D)		Unlike horses, humans have two eyes located side-by-side in the front of their heads. Thanks to the close side-by-side positioning, each eye takes a view of the same area from a slightly different angle. The two eye views have plenty in common, but each eye picks up visual information the other doesn't. Each eye captures its own view and the two separate images are sent on to the brain for processing. Binocular vision results when the brain combines these disparate images to determine true stereoscopic depth. Basically, the farther away an object is from you, the more similar the view in your two eyes, and the closer the object is to you, the more disparate the two images. The two images are united into one 3-d picture. The word "stereo" comes from the Greek word "stereos" which means firm or solid. With stereo vision you see an object as solid in three spatial dimensions - width, height and depth - or x, y and z. It is the added perception of the depth dimension that make stereo vision so rich and special.
stereo vision has many advantages		With stereo vision, we can see WHERE objects are in relation to us with much greater precision - especially when those objects are moving toward or away from us. We can see a little bit around solid objects without moving our heads and we can even perceive and measure "empty" space with our eyes and brains.