When the eyes converge, 
the directions of gaze of the two 
eyes form a particular angle 
with respect to one another, a 
kind of triangulation. If the 
object is near, this angle will 
be relatively large; if the object 
is far, the angle will be more 
acute. At infinity, the 
directions of gaze would be 
parallel and the angle would be 
zero, as can be seen in the 
illustration to the left. 

Angle of convergence of the 
eyes at infinite, far, and near 
distances.

Thus, the convergence (or, 
more generally, just vergence) 
angle of the eyes could be a cue 
to distance if the perceptual 
system receives information 
about the degree of 
convergence of the eyes and 
can interpret it appropriately. 
This kind of information 
concerns the absolute distance 
of a single object from us. I will 
refer to this aspect of 
perception as distance.