Involuntary eye responses as measures of fatigue in US Army Apache aviators.

INTRODUCTION AH-64 Apache helicopter pilots fly the aircraft using a monocular helmet-mounted display that provides imagery from two separate forward-looking infrared sensors mounted on the nose of the aircraft. Studies have documented complaints of fatigue, headaches, and visual problems associated with the use of this sighting system. The goals of this study were: 1) to quantify possible flight-induced fatigue in Apache aviators; and 2) to evaluate minimally intrusive neurophysiologic measures of fatigue for potential use in operational environments. METHODS Using a pre/post design, we assessed self-reported levels of alertness, physical, cognitive, and visual fatigue, and ocular indices of fatigue obtained using an instrument specifically designed to capture various eye responses. Data were contributed to this study by 53 aviators. RESULTS Significant differences in all pre- and postflight ocular responses were observed. Pupil size and constriction latency increased while constriction amplitude and saccadic velocity decreased. Significant pre- and postflight differences were also seen on all self-report measures. Pilots reported being less alert and more fatigued following flight. CONCLUSIONS We found that flight in an AH-64 Apache was a significant factor in producing changes in ocular and self-report measures similar to those produced by sleep loss.