Stereopsis refers to the case in which both eyes are fixated on the same object, resulting in a single perceived image. Two kinds of vergence motions occur to align the eyes with an object. See Figure 5.20. If the object is closer than a previous fixation, then a convergence motion occurs. This means that the eyes are rotating so that the pupils are becoming closer. If the object is further, then divergence motion occurs, which causes the pupils to move further apart. The eye orientations resulting from vergence motions provide important information about the distance of objects.