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Impaired Motion Perception in the Fellow Eye of Amblyopic Children is Related to Abnormal Binocular Function

Eileen E. Birch, PhD; Reed M. Jost, MS; Yi-Zhong Wang ,PhD; Krista R. Kelly, PhD; Deborah E. Giaschi, PhD
Retina Foundation of the Southwest, Dallas, TX, Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, Departments of Psychology and Ophthalmology, University of British Columbia,  Vancouver

Introduction:  While the clinical focus for amblyopia has been monocular patching to restore visual acuity of the amblyopic eye, recent evidence supports the primary role of binocular dysfunction in amblyopia. Binocular discordance due to strabismus, anisometropia, or both result not only in a monocular visual acuity deficit, but also fellow eye motion perception deficits.1 Here we examine these deficits and their relationship with clinical and sensory factors.

Methods:  73 amblyopic children (6-12y; 0.2-1.5 logMAR) with strabismus (n=18), anisometropia (n=32), or both (n=23) participated, along with 19 age-similar controls.  Performance on a motion-defined form (MDF) task was evaluated in the context of a Star Wars game. The child viewed an array of moving white dots on a black background; dots within a stationary rectangle (‘the enemy spaceship’) moved coherently in one direction, and dots outside moved in the opposite direction. The child’s task was to indicate the orientation of the enemy spaceship. The proportion of coherently moving dots was progressively reduced to determine the minimum coherence needed to perform the task.

Results:  MDF deficits were present in 82% of amblyopic eyes and 21% of fellow eyes.  Amblyopic eye MDF deficits correlated with suppression severity (p=0.0001), amblyopic eye visual acuity (p<0.0001), stereoacuity (p<0.0001), and W4 fusion (p<0.0001).  Fellow eye MDF deficits correlated with stereoacuity (p=0.0004) and W4 fusion (p=0.002).  Children receiving binocular amblyopia treatment had milder fellow eye MDF deficits than children treated with patching (p=0.03).

Discussion:  Fellow eye MDF deficits are common and likely reflect abnormalities in binocular cortical mechanisms that result from early discordant visual experience.

Conclusion:  Binocular amblyopia treatment, which is effective in improving visual acuity,2,3 may also provide a benefit for binocular function.

References:
1. Meier K, Giaschi D.  Unilateral amblyopia affects two eyes: fellow eye deficits in amblyopia.
Invest Ophthalmol Vis Sci 2017; 58:1779-1800
2. Kelly KR, Jost RM, Dao L, Beauchamp CL, Leffler JN, Birch EE.  Binocular iPad game vs patching for treatment of amblyopia in children: a randomized clinical trial. JAMA Ophthalmol 2016;134:1402-8.
3. Birch EE, Li SL, Jost RM, Morale SE, De La Cruz A, Stager D Jr, Dao L, Stager DR Sr  Binocular iPad game vs patching for treatment of amblyopia in children: a randomized clinical trial. J AAPOS 2015;19:6-11

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