Does infantile esotropia arise from a dissociated deviation?

Tonus refers to the effects of baseline innervation on musculature in the awake, alert state.(1) Since the normal anatomical resting position of the eyes is one of exodeviation, extraocular muscle tonus plays a vital physiologic role in establishing ocular alignment. Under normal conditions, binocular esotonus is superimposed on the baseline anatomical position of rest to maintain approximate ocular alignment, save for a minimal exophoria that is easily overcome by active convergence. When binocular visual input is preempted early in life, monocular fixation may give rise to a larger dissociated esotonus that gradually drives the 2 eyes into a "convergent" position, resulting in infantile esotropia.(2).