A novel automatic procedure for measuring ocular counterrolling: A computeranalytical method to determine the eye’s roll angle while subjects work on perceptual tasks

Abstract

In investigations ofthe perception ofspace, the consideration of ocular counterrolling-the movement of the eye around its visual axis in response to body movement-is crucially important. The angle ofthis movement must be known in order for one to determine the precise retinal coordinates of a distal object. Following transformation, this stimulus serves as a reliable cue for visual direction. The otolith organs provide information about body tilt and are responsible for ocular counterrolling. A novel, noninvasive method to measure ocular counterrolling, based on the cross-correlation of digitized video pictures of the eyes, is presented. The resolution attained was :s0.1°. The computer analysis is fully automatic and fast, and it can be performed while subjects work on perceptual tasks. No direct access to the eyeballs is required. Data from 4 subjects showing the counterrolling profile in various body positions are presented. 433We are primarily interested in spatial orientation, and particularly in vertical perception. To investigate this phenomenon further, we bring our human subjects into various body positions in a dark environment, where they are presented with a luminous line. The subjects are requested to set this luminous line to the apparent vertical.A system-analytical approach, as initiated by Bischof and Scheerer (1970), envisages the problem of the perception of the vertical as a compensatory process. The angle of body tilt, it has been argued, has to be compensated for by central-nervous processing (Bischof, 1966).The position of the line with respect to the body position allows us to calculate the angular deviation of the subjective vertical from the gravity vector (see Figure 1). In order to determine the precise compensatory angle usedThe authorsare gratefulfor the assistance of Walter Schmidand Henri Gossweiler, who built most of the technical equipment. We thank Christopher Pryce for critical reading of the manuscript and his helpful suggestions. Special thanks are also due to the subjects who patiently took part in the experiments. Anyone who is interested in applying the presented algorithmshouldcontactthe authors. The programsare written in FORTRAN 77 using specific routines to access the video digitizer. We plan to adapt the software to Apple Macintosh computers with the appropriate hardware for video digitizing. Requests for reprints should be sent to

Reading tilted: Does the use of tablets impact performance? An oculometric study

“…It was based on the algorithm described by Bucher, Heitger, Mast, and Bischof (1990). Circular profiles were recorded on the picture of the iris, around the center of the pupil.…”

Does the world rock when the eyes roll?

“…Ocular torsional position: The onboard optical components in the centrifuge, the procedure and the algorithm to determine the OCR have been fully described elsewhere (Bucher, Heitger, Mast, & Bischof, 1990). Briefly, the subject's head was stabilized by a removable bite-board with individual dental impressions.…”

Human perception of verticality: Psychophysical experiments on the centrifuge and their neuronal implications

“…They observed that the preferred position for adjusting the SVV sometimes sticks out of the subject's frontal plane even though the body is tilted in roll only. A detailed description of the apparatus used in this study is given elsewhere (Bucher, Heitger, Mast, & Bischof, 1990). …”