December 2022
Volume 22, Issue 14
Open Access
Vision Sciences Society Annual Meeting Abstract  |   December 2022
Eccentricity driven modulations of visual crowding across the central fovea
Author Affiliations & Notes
  • Ashley M. Clark
    University of Rochester
  • Martina Poletti
    Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA 94720
  • Footnotes
    Acknowledgements  NIH R01 EY029788-01
Journal of Vision December 2022, Vol.22, 3716. doi:
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      Ashley M. Clark, Martina Poletti; Eccentricity driven modulations of visual crowding across the central fovea. Journal of Vision 2022;22(14):3716.

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      © ARVO (1962-2015); The Authors (2016-present)

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It is well established that surrounding a stimulus with flankers decreases acuity, a phenomenon known as visual crowding. While it has been widely documented that the magnitude of crowding increases with eccentricity, it remains unknown if this increase starts already within the central 1-deg foveola, and if so, what is the rate of growth at this scale. Addressing this question is important as foveal vision is often confronted with crowded stimuli. We measured subjects’ (N=6) visual acuity in a 4AFC task. Stimuli were viewed monocularly in either isolation or with surrounding flankers and were presented at different foveal and extrafoveal eccentricities. Stimuli were presented in Pelli font, designed for testing foveal crowding, and their widths, ranging from 0.4' to 4.5', were adjusted using an adaptive procedure. Eye movements were measured with high-precision using digital Dual Purkinje Image eye-tracking. To limit visual stimulation around the desired foveal eccentricity, we used a state-of-the-art custom-made gaze-contingent display system allowing for more accurate gaze localization and retinal stabilization. Our results show that the impact of crowding increases with eccentricity already within the foveola; acuity in the presence of flankers decreases as a function of foveal eccentricity, with a decrease of 32% at the center of gaze, and an additional 24% drop as early as 10’ away. Further, crowding increases with eccentricity at a rate that is three times slower in the foveola (from 0-0.4 deg) than extrafoveally (from 1-6 deg). These findings reveal that visual crowding does not affect the whole foveola equally; its impact significantly increases even with minute changes in eccentricity. Therefore, under normal viewing conditions with crowded foveal stimuli, acuity likely drops considerably even a few arcminutes away from the preferred locus of fixation.


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