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S. Gowrisankaran, N. Fogt; Ocular Torsion and Associated Head Movement in a Flight Simulator. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2877.
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In previous studies, head tilt in the direction of a tilting horizon has been demonstrated in a flight simulator. Torsional eye movements during movement of the horizon in a flight simulator have not been examined. The purpose of this study was to measure ocular torsional responses to a moving horizon in a static flight simulator.
5 subjects (18-35 yrs) participated. Subjects viewed a projected scene (of the sky and the ground) in a dark room. Eye and head movements were recorded using a video tracker and a magnetic sensor respectively. 10 trials were recorded for each subject. In each trial subjects tilted the airplane/horizon (using a joystick) randomly to the right or left away from the horizontal meridian (aligning tilt), and returned the plane to a non-tilted horizontal position (realigning tilt). The movement of the horizon was recorded. The average frequency of these sinusoidal movements was 0.3 Hz.
3D eye and head movements for 20 blink free (20 aligning and 20 realigning tilts) trials were analyzed. The average magnitude of aligning tilt was 48deg and was 55deg for the realigning tilt. An ocular torsional response occurred with tilt of the horizon in 32 out of 40 cases. Head tilts (always in the direction of horizon tilt) occurred in 28 of the 40 cases analyzed. The average head tilt was 11.7deg for the aligning tilt and 8.7deg for the realigning tilt. Regardless of whether the head moved the typical torsional response was a high velocity movement in the same direction and faster than the horizon tilts, with an amplitude gain of 0.07. This was followed by a drift opposite to the initial movement. The average fast phase amplitude was 3.9 deg (aligning tilt), and 3 deg (realigning tilt).
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