June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
The effect of anisometropia on reflex vergence movements
Author Affiliations & Notes
  • Clara Mestre
    School of Optometry, Indiana University, Bloomington, Indiana, United States
  • Sonisha Neupane
    Department of Psychology, Northeastern University, Boston, Massachusetts, United States
  • Kathryn Bonnen
    School of Optometry, Indiana University, Bloomington, Indiana, United States
  • Laurie M. Wilcox
    Centre for Vision Research, York University, Toronto, Ontario, Canada
  • Deborah Giaschi
    Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
  • T Rowan Candy
    School of Optometry, Indiana University, Bloomington, Indiana, United States
  • Footnotes
    Commercial Relationships   Clara Mestre None; Sonisha Neupane None; Kathryn Bonnen None; Laurie M. Wilcox None; Deborah Giaschi None; T Rowan Candy None
  • Footnotes
    Support  NEI: R01 EY014460 (TRC)
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 2776 – A0311. doi:
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      Clara Mestre, Sonisha Neupane, Kathryn Bonnen, Laurie M. Wilcox, Deborah Giaschi, T Rowan Candy; The effect of anisometropia on reflex vergence movements. Invest. Ophthalmol. Vis. Sci. 2022;63(7):2776 – A0311.

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

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Purpose : Anisometropia is a risk factor for atypical binocular development associated with strabismus and amblyopia. The goal of this study was to understand the impact of different degrees of simulated anisometropia on vergence eye movements.

Methods : Participants viewed a cartoon character (2deg wide) displayed dichoptically on a 68x41deg gray background with varying amounts of retinal disparity. Spherical defocus of 1, 2 or 4D was applied to one or both eyes’ stimuli using convolution with the Point Spread Function adjusted for the subject’s pupil size. Eye movements were recorded with an Eyelink 1000. In condition 1, a step change in disparity (0-8deg) was introduced and displayed for 320ms, followed by a blank screen. Open-loop vergence amplitude was used to estimate the reflex response. In condition 2, retinal disparity varied between ±4deg relative to the screen with quasi-random velocities for 40s. Cross-correlations between stimulus and vergence velocities were computed.

Results : 22 youth and adults (15-51yrs) and 16 typically developing children (4-8yrs) participated in condition 1. With no defocus, open-loop vergence peaked for ±2deg disparity for both groups. Median (IQR) amplitudes were similar at 0.33 (0.19) deg convergence and -0.40 (0.23) deg divergence for adults, and 0.50 (0.51) deg and -0.42 (0.43) deg for children. Bilateral defocus had no effect. However, 4D of unilateral defocus reduced convergence and divergence amplitudes, especially for children (0.28 (0.33) deg and -0.36 (0.30) deg, respectively). Condition 2 was completed by 18 typical youth and adults (16-53yrs). The median (IQR) peak correlation of 0.61 (0.14) with no defocus decreased to 0.33 (0.41) with 4D unilateral defocus, while the decrease was smaller with 4D bilateral defocus (0.57 (0.23)). The median (IQR) latency of 183 (40) ms with no defocus increased to 198 (40) ms and 223 (40) ms with 4D of bilateral and unilateral defocus, respectively.

Conclusions : Our results confirm that unilateral defocus has a more detrimental effect than bilateral defocus on reflex vergence movements especially in children, which emphasizes the importance of similar retinal images for binocular development. For adults, the sustained responses required in condition 2 were especially affected. Although 1D of anisometropia can be associated with amblyopia, 2 to 4D are needed to disrupt this reflex oculomotor system and compromise accurate alignment for this small central stimulus.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.


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