Hysteresis in ocular torsion under varying luminance.

K. F. Arrington,     B. J. Pierce,     M. A. Moreno

Investigative Ophthalmology & Visual Science,
1998; 39(4). Abstract nr 2900, p. S623


Purpose. Prior studies report that rotation disparities affect ocular torsion and central re-normalization of the depth space. In turn, these factors affect perceived inclination of stereo images. We examine the effects of varying luminance of a zero-disparity superimposed pattern (R0), on the perceived inclination of a 4 degree rotation-disparity pattern (R4). Methods. Each stereo image included two arrays (R0 & R4) of randomly distributed texture elements (crosses, squares, circles, and lines) subtending 60H x 50V degree visual angle, which yielded two depth planes. Luminance of the R0-plane varied either as (a) random trials, or (b) a continuous cosine function of time. Results. Results show that inclination perception is a linear function of luminance under random trials and during increasing luminance trials, but shows substantial hysteresis during decreasing luminance trials. Conclusion. Ocular torsion (and central mechanisms that are responsible for nulling rotation disparities), can be incrementally adjusted by a contradictory stimulus as the energy of that stimulus increases, however there is substantial hysteresis for a given ocular torsion when the energy of a contradictory stimulus decreases. The system seems to be efficient in adapting to the introduction of new information, but robust against the diminution of that information, as would occur during normal fluctuations in viewing.

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