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Susana Chung, Jean-Baptiste Bernard, Girish Kumar, Anirvan Nandy, Bosco Tjan; The two-dimensional shape of the crowding zone following macular lesions. Journal of Vision 2014;14(10):768. doi: https://doi.org/10.1167/14.10.768.
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The crowding zone, the region over which spatial interaction of nearby objects occurs, is known to be isotropic in shape in the normal fovea, and anisotropic in the normal periphery, with the major axis oriented toward the fovea. Recently, Nandy and Tjan (2012) attributed the anisotropic shape of the crowding zone in the normal periphery to saccadic eye movements. A prediction from their theory is that people whose saccadic eye movements are referenced to a non-foveal retinal location should show corresponding changes in the shape of the crowding zone at this location, and at other peripheral locations. To test this prediction, we mapped the two-dimensional shape of the crowding zone for three observers with macular lesions who demonstrated a consistent re-referencing of saccades toward their non-foveal preferred retinal locus (PRL), at their PRL and at another peripheral (para-PRL) location. To map the crowding zones, we determined the critical spacing between a target letter (presented at the PRL or at a fixed para-PRL location) and its flankers that yielded 71% correct identification of the target letter, along different meridians with respect to the target. Stimuli were presented using a scanning laser ophthalmoscope that allowed us to present stimuli at precise retinal locations while obtaining behavioral responses from the observers. Our results showed that for all observers, the crowding zone at the PRL was significantly less anisotropic than would be expected based on the normal periphery. At the para-PRL location, the crowding zone was irregular in shape, but could be well described by two superimposed ellipses with one oriented toward the PRL and the other toward the non-functioning anatomical fovea. Our results provide the first set of psychophysical evidence linking the re-referencing of saccadic eye movements with the modification of spatial properties at and around the PRL for people following macular lesions.
Meeting abstract presented at VSS 2014
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