Extraocular proprioception is required for spatial localization in man.

We studied the effect of extraocular muscle deafferentation on the performance of manual pointing to foveated visual targets at different craniotopic locations. Five patients who underwent unilateral thermocoagulation of the trigeminal nerve (V) for trigeminal neuralgia were tested before and after surgery. Only the group of patients with postsurgical corneal anaesthesia, attesting to involvement of the ophthalmic branch (which carries the ocular proprioceptive fibres), presented deficits in accuracy of pointing. The position of initial and final pointing was shifted toward the lesioned side predominantly in the ipsilateral hemispace. These data support a model in which balanced ocular proprioceptive inputs are required for accuracy of visually guided movements in egocentric space.