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Andrew Haun, Eli Peli; Binocular Rivalry with Peripheral Prisms for Treatment of Hemianopia. Journal of Vision 2012;12(9):211. doi: https://doi.org/10.1167/12.9.211.
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© ARVO (1962-2015); The Authors (2016-present)
A visual aid for individuals suffering from hemifield loss due to stroke or brain injury uses high power prism segments to shift a region of the blind field into the seeing field’s periphery, making it possible for a patient to detect obstacles that otherwise would go unseen. The prisms are usually applied monocularly, which introduces binocular conflict. Since the prism slightly degrades the shifted image, the prism-image could be disproportionately suppressed, and its utility reduced. This has not been found to be the case using abruptly presented probe targets, but real-world obstacles rarely appear abruptly. Here we evaluate binocular rivalry through the prism aid, using stimuli that more closely represent some of the spatiotemporal properties of real-world scenes. Normally-sighted subjects centrally fixated a display through a pair of spectacles to which binocular occluders had been affixed to occlude one side of the visual field in both eyes. On one lens, a 20° Fresnel prism was affixed, shifting content from the occluded field into the seeing field periphery. Corresponding peripheral retinal positions were located so that one eye viewed a target normally while the other eye viewed a target through the prism. Targets were opponent-colored 5° patches of texture (1/f noise or bicolor edge textures) drifting away from the display center, surrounded either by in-phase monochromatic texture filling the ipsilateral display or by a blank field. Subjects tracked the binocular rivalry induced by continually indicating which color (or mixture) was seen during a 30 second recording period. We found that for isolated (no-surround) targets, prism-image predominance could be as low as 10-15%. However, when contrast structure surrounded the targets, prism-image predominance increased, under some conditions achieving parity (40-45%) with the normally-viewed image. We conclude that moving, densely-textured imagery is not roundly suppressed despite the degradation caused by the Fresnel prism.
Meeting abstract presented at VSS 2012
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