Proprioceptive knowledge of eye position.
The peripheral and central apparatus for extraretinal (non-visual) sensing of eye position by proprioception (inflow) is documented. The functional significance of this inflowing signal is shown by its role in (1) providing oculomotor stability in fixation and conjugacy, (2) specification of visual direction, (3) development of some visual functions, and (4) depth and vergence responses. Inflow is seen as a slowly-operating calibrator of eye position, with outflow signals read out from the underlying inflow signal. Good "preparations" for studying inflow include humans having their extraocular muscles surgically manipulated in some way for treatment, or those with some deficit in the afferent pathways. A complete understanding of the oculomotor system, in normal and pathological conditions, demands the inclusion of inflow.