February 2022
Volume 22, Issue 3
Open Access
Optica Fall Vision Meeting Abstract  |   February 2022
Contributed Session I: The effect of spherical defocus on vergence and diplopia in adults and children
Author Affiliations
  • Clara Mestre
    School of Optometry, Indiana University, USA
  • Sonisha Neupane
    School of Optometry, Indiana University, USA
  • Deborah Giaschi
    Department of Ophthalmology and Visual Sciences, University of British Columbia, Canada
  • Laurie M. Wilcox
    Centre for Vision Research, York University, Canada
  • T. Rowan Candy
    School of Optometry, Indiana University, USA
Journal of Vision February 2022, Vol.22, 10. doi:https://doi.org/10.1167/jov.22.3.10
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      Clara Mestre, Sonisha Neupane, Deborah Giaschi, Laurie M. Wilcox, T. Rowan Candy; Contributed Session I: The effect of spherical defocus on vergence and diplopia in adults and children. Journal of Vision 2022;22(3):10. doi: https://doi.org/10.1167/jov.22.3.10.

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

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Abstract

Anisometropic children (with unequal refractive error in the two eyes) are at risk for strabismus or amblyopia. We simulated unilateral and bilateral spherical defocus to clarify the link between anisometropia, vergence eye movements and the perception of single vision. Adults (N=20, 15-51 yrs) and typically developing children (N=9, 5-8 yrs) viewed a dichoptic cartoon character presented in the fixation plane. Step changes in disparity of between 0 and 8 deg were introduced for 320 ms, followed by a blank screen. Vergence responses were recorded with an Eyelink 1000 and subjects reported whether they perceived a single (fused) or double (diplopic) character. Spherical defocus from 0.5 to 4D was applied to one or both eyes’ stimuli using convolution of the point spread function for the subject’s pupil size. Open loop vergence amplitude was used to estimate the reflex response (without feedback). For no defocus, open loop vergence peaked at +/-2 deg disparity with amplitudes of 0.29 deg convergence and -0.44 deg divergence for adults, and 0.56 deg and -0.46 deg for children. Bilateral defocus had no effect on this reflex response; however, 4D unilateral defocus significantly reduced vergence amplitudes in both age groups with no corresponding change in diplopia thresholds. Our results confirm that anisometropic blur is particularly disruptive to reflex vergence responses, which could limit the accurate realignment of the eyes and lead to atypical binocular development.

Footnotes
 Funding: The project was supported by R01 EY014460 (TRC) and a EY019008 (P30) to Indiana University.
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