We have two eyes which allow us to see in stereovision. Our eyes are close to each other (5 cm apart), but not in the exact same spot, therefore each eye sees an object at a slightly different angle. Each eye sees a different view and both views are transmitted to the brain for processing. The brain then unites these images and overlaps them, creating one picture (5).  The difference in view is shown below. As you can see at point A, the nose hinders our ability to see some images and motion.  The difference between the centerline of the eyes’ lens is B.  This difference leads to the location of the image in the field of view of one eye to be different than the other eye (3).  Combining these images leads to depth perception and allows us to see objects in three dimensions

 

 The optic nerves cross over at the optic chiasma.  The lateral nerve of each eye does not cross over but the medial nerve does.  This causes the right side of the brain to receive information from the right side of both eyes. Therefore, there appears to be no crossing over. But the lens of the eye makes it so objects on the right side of the retina are from the left side of the field of view.

 

 

Stereovision helps us to see where objects are relative to our bodies with great precision.  Stereo vision is especially useful when objects are moving away from us or toward us. Because of stereovision, we can see a  around a three dimensional solid object without turning our heads, and we can see empty space (5).

Not convinced that stereovision is important? Have someone throw a ball at you, and try to catch it while you have one eye closed.