Performance-based assessment of oculomotor efficiency.

Acquisition of visual information from spatial points disparate enough to necessitate head and eye movement involves the vestibular and other oculomotor control systems in shifting and stabilizing gaze relative to those points. In the present study, a simple procedure to test oculomotor abilities was developed and evaluated; it uses performance (serial letter identification) to maintain initial gaze position and performance (number of digits correctly identified) to measure the efficiency of gaze-shift control. Number of digits acquired from briefly displayed digit sets was consistently and powerfully influenced by exposure duration of digit sets and to a lesser extent by the size of required gaze shift. The performance of normal subjects in eye movement and head-and-eye movement conditions is predictable from static performance of normals. Results suggest that the procedure will be sensitive to certain types of central nervous system and vestibular pathology. Substantial individual differences in performance dependent upon gaze-shift control were found among normal subjects. If some pilots operate at the lower extremes of the performance distribution, they may be subject to critical response deficiencies in emergency conditions requiring large gaze shifts.