Our both eyes can move in all the four directions to see near objects. Even if we close one eye and see with other eye, the eyeball of the closed eye also moves with the open eye in the direction of the object. Thus when we direct our eyes to look at an object near 'or, at a distance, the two eyes always converge simultaneously. This co-operation between both the eyes develope from childhood. Thus, sensations in the eye movements are important cues for interpretation of depth.