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Open AccessArticle

An Unexpected Spontaneous Motion-In-Depth Pulfrich Phenomenon in Amblyopia

McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, QC H3G 1A4, Canada
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Vision 2019, 3(4), 54; https://doi.org/10.3390/vision3040054
Received: 28 May 2019 / Revised: 30 September 2019 / Accepted: 18 October 2019 / Published: 22 October 2019
The binocular viewing of a fronto-parallel pendulum with a reduced luminance in one eye results in the illusory tridimensional percept of the pendulum following an elliptical orbit in depth, the so-called Pulfrich phenomenon. A small percentage of mild anisometropic amblyopes who have rudimentary stereo are known to experience a spontaneous Pulfrich phenomenon, which posits a delay in the cortical processing of information involving their amblyopic eye. The purpose of this study is to characterize this spontaneous Pulfrich phenomenon in the mild amblyopic population. In order to assess this posited delay, we used a paradigm where a cylinder rotating in depth, defined by moving Gabor patches at different disparities (i.e., at different interocular phases), generates a strong to ambiguous depth percept. This paradigm allows one to accurately measure a spontaneous Pulfrich phenomenon and to determine how it depends on the spatio-temporal properties of stimulus. We observed a spontaneous Pulfrich phenomenon in anisometropic, strabismic, and mixed amblyopia, which is posited to be due to an interocular delay associated with amblyopic processing. Surprisingly, the posited delay was not always observed in the amblyopic eye, was not a consequence of the reduced contrast sensitivity of the amblyopic eye, and displayed a large variability across amblyopic observers. Increasing the density, decreasing the spatial frequency, or increasing the speed of the stimulus tended to reduce the observed delay. The spontaneous Pulfrich phenomenon seen by some amblyopes was variable and depended on the spatio-temporal properties of the stimulus. We suggest it could involve two conflicting components: an amblyopic delay and a blur-based acceleration. View Full-Text
Keywords: Pulfrich phenomenon; interocular delay; stereopsis; motion in depth; amblyopia Pulfrich phenomenon; interocular delay; stereopsis; motion in depth; amblyopia
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Reynaud, A.; Hess, R.F. An Unexpected Spontaneous Motion-In-Depth Pulfrich Phenomenon in Amblyopia. Vision 2019, 3, 54.

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