Fig. 15 Basic closed-loop block diagram of the vergence subsystem (heavy lines) superimposed on the block diagram of the total ocular motor control system. The control signal, disconjugate retinal error (static diplopia), and/or error velocity (changing diplopia) is sensed by the cortex. The decision to move the eyes is forwarded to a midbrain generator where the motor commands are initiated and passed to the ocular motor nuclei (OMN). This innervation causes the extraocular muscles (EOM) to move the eyes with a VEM and change relative eye position and/or velocity. Assuming no change in head position, this new absolute eye position and/or velocity sums with target position and/or velocity to produce zero disconjugate retinal error(s).