# The role of eye-movements in limiting spatial vision in amblyopia

> **NIH NIH R21** · UNIVERSITY OF CALIFORNIA BERKELEY · 2020 · $271,185

## Abstract

Levi, Dennis M.
PROJECT SUMMARY/ABSTRACT
 Amblyopia is a developmental disorder of spatial vision usually associated with the presence of strabismus,
anisometropia or form deprivation early in life. It affects visual acuity, contrast sensitivity and position acuity.
Amblyopia is clinically important because, aside from refractive error, it is the most frequent cause of vision loss
in infants and young children, and amblyopia is of basic interest because it reflects the neural impairment which
can occur when normal visual development is disrupted. The long-range objectives of this research are to
understand the mechanisms that limit spatial vision in humans with amblyopia, with the ultimate goal of
developing new approaches aimed at more effective treatment.
 While our focus in past studies has been on the sensory losses, here we propose the application of a
number of innovative methods that will enable us to test specific hypotheses about the role of eye-movements
in limiting spatial vision in amblyopia.
 Aim 1 tests the hypothesis that abnormal spatial vision is at least in part a consequence of fixational eye
movements. Specifically we ask how both the retinal image motion induced by these abnormal fixational eye
movements, and the eye movements per se, influence visual resolution, visual acuity, crowding and the
precision and accuracy of spatial localization. We will use a high-resolution video eye tracker, the Tracking
Scanning Laser Ophthalmoscope (TSLO) which allows stimuli to be delivered to precisely identifiable locations
on the retina, to test our hypothesis using three different approaches: i) We will measure, model and
characterize fixational eye movements in normal and amblyopic adults while performing visual tasks that are
compromised in amblyopia. ii) We will assess the role of retinal image motion by comparing visual performance
on these tasks under stabilized, unstabilized and “playback” (i.e., superimposing the amblyopic eye's retinal
image motion on the nonamblyopic eye) conditions. iii) We will assess the role of eye movements per se by
evaluating visual performance around the time of occurrence of drifts and microsaccades.
 Compared to normal observers, strabismic amblyopes have significantly longer saccadic and manual
latencies to stimuli seen with their amblyopic eyes, compared to their fellow eyes. Aim 2 tests the hypothesis
that for strabismic amblyopes, the frequent microsaccades and accompanying saccadic suppression and
attentional shifts made while strabismics struggle to maintain fixation with their amblyopic eyes, result in all
types of reaction times being irreducibly delayed, commensurate with the degree of unsteadiness. Because the
degree of unsteadiness is correlated with LogMAR acuity, it follows that reaction time and saccadic latency are
also correlated with LogMAR acuity. Aim 2 tests a number of specific hypotheses regarding the role of
microsaccades in reaction time and visual search.
1

## Key facts

- **NIH application ID:** 9993530
- **Project number:** 5R21EY030609-02
- **Recipient organization:** UNIVERSITY OF CALIFORNIA BERKELEY
- **Principal Investigator:** Dennis Michael Levi
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $271,185
- **Award type:** 5
- **Project period:** 2019-09-01 → 2023-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9993530

## Citation

> US National Institutes of Health, RePORTER application 9993530, The role of eye-movements in limiting spatial vision in amblyopia (5R21EY030609-02). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/9993530. Licensed CC0.

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