Anomalous and normal motor fusion in esophoria and microesotropia

Certain cases of esophoria and microesotropia have common characteristics: a small manifest deviation (called fixation disparity in esophoria), increase of the angle after occlusion, and convergent motor fusion in the presence of a persistent esodeviation. Convergent motor fusion with conservation of the esodeviation is anomalous motor fusion in which the zero point is situated at the binocular pseudofovea. The increase of the angle after occlusion, however, points to a rudiment of normal motor fusion with its zero point at zero disparity. The findings in esophoria and microstrabismus can be explained from sensory-motor factors. The hypothesis of anatomical factors is superflous.