CONVERGENCE 

The other factor based on 
binocular vision, convergence, 
is the angle formed by the two 
eyes looking directly at, or 
fixating, a given point in space. 
The gaze of each of our eyes 
normally tends to converge on 
the same point.

    If the eyes behaved 
independently of one another, 
an object's image would fall in 
entirely different positions on 
each retina, which would 
result in double vision. 
Singleness of vision depends 
upon the imaging of the same 
objects on corresponding points 
of the two retinas. The reason 
for this is that the light-
sensitive cells in the retinas, 
the rods and cones that are in 
such corresponding places in 
each eye, give rise to neural 
signals that travel along fibers 
that ultimately end up in 
roughly the same region of the 
visual cortex of the brain.