0186 OCULOMOTOR BEHAVIOR METRICS CHANGE ACCORDING TO CIRCADIAN PHASE AND TIME AWAKE

Abstract

Introduction: There is a need for non-invasive, objective measures to forecast performance impairment arising from sleep loss and circadian misalignment, particularly in safety-sensitive occupations. Eyetracking devices have been used in some operational scenarios, but such devices typically focus on eyelid closures and slow rolling eye movements and are susceptible to the intrusion of head movement artifacts. We hypothesized that an expanded suite of oculomotor behavior metrics, collected during a visual tracking task, would change according to circadian phase and time awake, and could be used as a marker of performance impairment. Method(s): Study participants completed two weeks of a stable schedule including 8.5 hours in bed at home, followed by a ~24-hour laboratory constant routine (CR) in semi-recumbent posture under < 4 lux of light. Snacks, saliva samples, and the psychomotor vigilance task (PVT) were collected hourly. The visual tracking task was collected at two, six, twelve, and sixteen hours after waking, then hourly. We assessed saccadic amplitude, pursuit latency, initial acceleration, steady-state pursuit gain, proportion of smooth tracking, noise in pursuit direction, noise in pursuit speed, and speed responsiveness. Melatonin was assayed and subjected to a best-fit cosine function to determine the acrophase. All data were analyzed using SAS and MatLab. Result(s): Twelve participants (mean age 25.0 y [+/- 5.6]; 6F) completed the study. Steady-state pursuit gain, saccadic amplitude, proportion of smooth tracking, direction noise, and speed noise each showed robust slowing, followed by partial recovery, coinciding approximately with circadian phase changes in melatonin amplitude and performance on the PVT. Other oculomotor metrics did not show changes during the CR. Conclusion(s): Several oculomotor behavior metrics change with circadian time of day and time awake. These measures show promise as indicators of performance impairment. Further study is required to determine whether such visual tracking tasks might be useful in determining fitness-for-duty in operational settings.