Changes in physiological parameters induced by optical misalignment in night vision binocular devices

摘要

Use of binocular night vision devices by military aircrew has been associated with visual fatigue. Misalignment betweenthe two binocular images may be one source of this fatigue and could degrade task performance. The eyes have somedegree of tolerance to optical misalignment; however, published tolerance limits vary widely and may have limitedrelevance for military pilots flying long missions. We used a simulated flying task to investigate the effect ofmisalignment on task performance and visual fatigue.A simulated helicopter flying task was presented simultaneously with three secondary tasks relevant to the visual,auditory, and cognitive demands experience by military aircrew. Task performance was objectively assessed usingtracking errors, response times and incorrect responses.Eight participants were exposed to a controlled level of optical misalignment by attaching customised lenses to a TobiiPro 2 eye tracker. The misaligned condition was compared with an aligned condition with identical workload. Pupildiameter, peripheral skin temperature and ECG data were collected during the task as objective markers of fatigue.Our results showed that misalignment induced significant degradation of task performance both in terms of longerresponse times and an increased number of incorrect responses. Misalignment was also associated with significantlyincreased fatigue as measured by reduction of peripheral skin temperature and pupil diameter. Moreover, typical taskrelated modulations in heart rate and heart rate variability were significantly impaired in the misaligned condition.