In recent experiments involving acceleration stimuli, researchers
instructed subjects to focus on a visual target while measuring the vestibulo-
ocular reflex (VOR) in one eye. These experiments showed conclusively
that the VOR is influenced by target distance. We, on the other
hand, were interested in investigating the VOR of subjects accelerated in
complete darkness. Specifically, we wished to determine the subject's
vergence point, which cannot be accomplished using data obtained from
only one eye. Hence, a binocular eye-tracking system that works in the
dark was required. In the experiment described in this thesis, the subject
was rotated in the dark on NAMRL's Coriolis Acceleration Platform. The
position of each pupil center was tracked and recorded by two helmetmounted
infrared cameras connected to a computer-controlled data
acquisition system. The position data were used to calculate the angles
through which the eyes rotated, and then trigonometric principles were
applied to construct the line of sight for each eye for any moment in time;
the intersection of these two lines is the vergence point. With the NAMRL
binocular eye-tracking system, an accelerating subject's vergence point
can accurately be determined if it is less than 1. 5 meters away. The vergence
data obtained from this experiment suggest that vergence distance
does not exclusively drive the VOR in the dark.
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