Proportionalregelung der Fusion, Integralregelung der willkürlichen Konvergenz

When, by a fusional stimulus, the eyes are brought into a position of vergence, there remains a steady-state error (proportional control system). In convergent positions this error can be reduced to zero by voluntary convergence. Voluntary convergence, and movements of gaze, have an integral control system without steady-state error. There are physiological and clinical proofs for this difference between fusional and voluntary convergence. In normal subjects the convergence can be measured with more or less influence of voluntary convergence. In cases of fusional weakness and trained convergence the error is small, in convergence weakness with good fusion it is large. Exceptionally large is the steady-state error of motor fusion in anomalous binocular vision.