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Helga Mazyar, Bosco Tjan; In search of the visual and oculomotor factors that determine the location of a preferred retinal locus. Journal of Vision 2016;16(12):1338. doi: 10.1167/16.12.1338.
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© ARVO (1962-2015); The Authors (2016-present)
Saccades bring objects of interest to the fovea. Losing foveal vision leads to the adoption of a preferred retinal locus (PRL) for fixations, sometimes with saccades re-referenced to the PRL. The retinal location of a PRL varies greatly across individuals. It is not known what visual and/or oculomotor factors may determine a PRL's location. Measuring these factors before the formation of a PRL had not been feasible. We developed a method that constrains PRL formation to a one-dimensional contour, in normally sighted participants. The method allows us to systematically measure visual and oculomotor characteristics along the contour before and after PRL formation. We assessed form vision (visual acuity, crowded visual acuity, position uncertainty) and oculomotor performance (peripherally guided fixation stability and saccade accuracy) of normally sighted participants at 8 evenly spaced locations on an imaginary circle, 6° radius and centered at the fovea. We used the Contact Task (Mazyar & Tjan, 2015 VSS) to induce a PRL. Participants had to move an opaque and gaze-contingent disc, 6° in radius and centered at the fovea, to make contact with a small target, which appeared at a random screen location in each trial. The participant had to establish contact between the edge of the disc and the target and maintain it for 500 ms before the target was dismissed and a new trial began. A preferred contact point (the induced PRL) naturally emerged and stabilized within 1000-2000 trials in all 3 participants, replicating our previous findings (7 out of 8 participants). The formed PRLs were in the lower (2 participants) or the left visual field. The rapid and stable formation of PRL suggests that underlying factors governing PRL formation should be crisp. However, none of our measured visual and oculomotor characteristics could predict PRL location. A larger study is needed.
Meeting abstract presented at VSS 2016
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