August 2023
Volume 23, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2023
Vergence anomalies are associated with impaired stereopsis in the central visual field
Author Affiliations & Notes
  • Aidan Gauper
    Smith-Kettlewell Eye Research Institute
  • Suzanne McKee
    Smith-Kettlewell Eye Research Institute
  • Dennis Levi
    UC Berkeley
  • Preeti Verghese
    Smith-Kettlewell Eye Research Institute
  • Footnotes
    Acknowledgements  NIH Grant 1R01EY034370
Journal of Vision August 2023, Vol.23, 5092. doi:
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      Aidan Gauper, Suzanne McKee, Dennis Levi, Preeti Verghese; Vergence anomalies are associated with impaired stereopsis in the central visual field. Journal of Vision 2023;23(9):5092.

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

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Previously we mapped stereopsis across the visual field and showed that local stereopsis is impaired in the central visual field for individuals with known stereo deficits due to anisometropia or microstrabismus, while peripheral stereopsis was spared. As disparity drives fusional vergence responses, we hypothesized that the residual sensitivity to coarse disparities in the near periphery likely drives fusional vergence eye movements. Furthermore, if stereopsis in the central foveal region is impaired, then the fusional vergence response to a small stimulus confined to the near foveal region will be reduced. We used binocular eye tracking (Eyelink 1000 in the table-mount configuration), to measure the vergence response to a disparity step as the difference in the right and left eye position signals. We measured vergence as a function of stimulus configuration and the size of the disparity step. The disparity step occurred on 3 configurations: a large disc 16°in diameter, a small disc 4° in diameter, and an annulus with outer and inner diameters corresponding to the large and small discs. After the observer aligned nonius lines, a key press initiated the disparity step that lasted 3 seconds. Individuals with anisometropia or microstrabismus (n=3) had low vergence gain for small stimuli, that sometimes increased to near normal levels for larger stimuli, consistent with abnormal stereopsis in the central visual field. Among controls with no history of amblyopia or strabismus (n=8), those with intact local stereopsis across the visual field had vergence gains near 1, for all stimulus sizes (n=4). However, the remaining observers were stereoanamolous in the central visual field, and had abnormal fusional vergence. These abnormalites were either transient (could be made normal with increased effort) or remained persistent. These results suggest that the stereo-deficiency in the central retina is associated with poor fusional drive.


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