Tracking with a restricted field of view: performance and eye-head coordination aspects

Vision through a restricted field of view (RFOV) is becoming increasingly common in aviation with the use of helmet mounted displays. Our first experiment investigated the influence of a narrow (20 degrees) binocular RFOV on performance during head-free visuo-manual tracking of a wide range (+/- 85 degrees) horizontally moving target. Second, the effects of two levels of RFOV (20 degrees, 70 degrees) on a similar tracking task presented with various eccentricities were compared to full field of view (FOV). Eye and head movement around the yaw axis were recorded and analyzed versus head-free visual pursuit alone. Tracking performance appeared moderately impaired when RFOV was set to 20 degrees, but did not improve with a 70 degrees field. Discomfort due to unusually large head movements was ruled out as a causal factor. Visuo-manual tracking apparently implies a need for head stability. RFOV degrades this basic requirement which, in turn, could explain performance impairment. Analysis of eye-head coordination characteristics following FOV task conditions supports this hypothesis.