Impaired Fellow Eye Motion Perception and Abnormal Binocular Function

Abstract

PURPOSE. Binocular discordance due to strabismus, anisometropia, or both may result in not only monocular visual acuity deficits, but also in motion perception deficits. We determined the prevalence of fellow-eye deficits in motion-defined form (MDF) perception, the ability to identify a two-dimensional (2D) shape defined by motion rather than luminance contrast. We also examined the following: the causative role of reduced visual acuity and binocularity, associations with clinical and sensory factors, and effectiveness of binocular amblyopia treatment in alleviating deficits. METHODS. Participants included 91 children with residual amblyopia (strabismic, anisometropic, or both; age, 9.0 6 1.7 years), 79 nonamblyopic children with treated strabismus or anisometropia (age, 8.5 6 2.1 years), and 20 controls (age, 8.6 6 1.5 years). MDF coherence thresholds, visual acuity, stereoacuity, and interocular suppression were measured. RESULTS. MDF deficits, relative to controls, were present in the fellow eye of 23% of children with residual amblyopia and 20% of nonamblyopic children. Stereoacuity and age first patched were correlated with MDF threshold (r ¼ 0.29, 95% CI: 0.09-0.47; r ¼ À0.33, 95% CI : À0.13 to À0.50, respectively). MDF deficits were more common in children treated with patching alone than in those receiving contrast-rebalanced binocular treatment with games or movies (t 89 ¼ 3.46; P ¼ 0.0008). The latter was associated with a reduction in mean fellow eye MDF threshold (t 26 ¼ 6.32, P < 0.0001). CONCLUSIONS. Fellow eye MDF deficits are common and likely reflect abnormalities in binocular cortical mechanisms that result from early discordant visual experience. Binocular amblyopia treatment, which is effective in improving amblyopic eye visual acuity, appears to provide a benefit for the fellow eye.

Suppression Rather Than Visual Acuity Loss Limits Stereoacuity in Amblyopia

“…[12][13][14][15] In addition to visual acuity and stereoacuity loss, amblyopia results in impaired position discrimination and contrast sensitivity 11 and, furthermore, may be associated with higher order functional and processing impairments that suggest visual neurodevelopmental retardation beyond the primary visual cortex. [16][17][18] Interocular suppression of visual information from the amblyopic eye is frequently reported in amblyopia, 13,19 presumably to compensate for conflicting visual input. 20 As well as limiting stereopsis by preventing sensory fusion, 21 the role that suppression plays in causing or limiting amblyopia recovery is yet to be fully determined.…”

“… 12 – 15 In addition to visual acuity and stereoacuity loss, amblyopia results in impaired position discrimination and contrast sensitivity 11 and, furthermore, may be associated with higher order functional and processing impairments that suggest visual neurodevelopmental retardation beyond the primary visual cortex. 16 – 18 …”

Fellow Eye Deficits in Amblyopia

“…(Figure 4) Fellow eye motion-defined form deficits have been reported to be resistant to rehabilitation by patching, 44 but were responsive to binocular amblyopia treatment. 46…”

“…Fellow eye motiondefined form perception deficits have been reported to be resistant to rehabilitation by patching 44 but responsive to binocular amblyopia treatment. 46 (Figure 7). More effective treatments for amblyopia may target suppression, by requiring integration of information between the two eyes to play dichoptic games or watch dichoptic videos.…”

Amblyopia, deprivation and health disparities research: challenges in 2020

“…When testing the individual, amblyopia is usually identified by reduced high-contrast visual acuity but contrast sensitivity, fixation stability, reading speed, and fine-motor coordination are also affected [5]. There are subtle, measurable impacts upon fellow-eye vision such as identification of a shape by motion, known as motion-defined form [6].…”