[Abstract Title]. - Society for Neuroscience

Topic: D.06.c. Eye and head control
Support: Austrian Science Fund (FWF L425-N15)
Upper Austrian University of Applied Sciences
Title: Optimizing video-oculographic (VOG) eye movement recordings of rapid head impulses
Authors: M. PLATZ 1 , J. SCHARINGER 2 , *T. P. HASLWANTER 1 ;
1 Med. Technol., Upper Austrian Univ. o Appl Sci., Linz, Austria; 2 Dept. of Computat.
Perception, Johannes Kepler Univ., Linz, Austria
Abstract: Video-based eye movement recording, often called "Video-Oculography" (VOG), is
replacing other techniques as the standard tool for measuring eye movements, for clinical
applications as well as for research. Since new types of video cameras now regularly offer
sampling rates above 100 Hz, the biggest remaining problem is the artifacts caused by camera
movement with respect to the head: an uncompensated camera movement of only 1mm causes
measurement errors of approximately 5deg. This is particularly important for VOG recordings
during "Rapid Head Impulses", a standardized procedure for testing the functional status of the
vestibular system: there camera slippage of a few millimeters is almost impossible to prevent.
The most successful approach to compensate camera slippage with respect to the head has been
utilization of the location of reflections of external illumination sources on the corneal surface.
This technique works well when illumination and camera are at a distance that is much larger
than the focal length of the camera. When camera and illumination are head-mounted, though,
the suitability of this approach has yet to be shown.
Using biomechanical simulations of the pupil center as well as of specular reflections of
illumination points on the human cornea, we investigate the suitability and the limitations of this
approach. In particular, we compare to which extent consideration of the actual corneal shape
and slippage path can improve the elimination of camera slippage during VOG recordings,
compared to more established approaches like linear or polynomial curves fit to the distance
between pupil center and corneal reflections.
For practical applications, our compensation scheme is applied to VOG recordings during rapid
head impulses. For VOG we use the "EyeSeeCam" system, which can provide 3D eye
movements at up to 500 Hz; the actual camera slippage is determined by measurements of 3D
head- and camera movement with a "Lukotronic" system; and the results are compared with our
compensation scheme, which tries to eliminate the camera slippage using only the information
from the video images.
Disclosures: M. Platz, None; J. Scharinger, None; T.P. Haslwanter, None.
Poster
263. Eye Movements: Eye and Head Control