Feature Counting Is Impaired When Shifting Attention Between the Eyes in Adults With Amblyopia

Attention deficits in Amblyopia: A narrative review

Amblyopia has effects on vision that extend from the processing of low-level visual features to higher level functions such as visual attention. In this narrative review, we focus on the impact of amblyopia on visual attention. A structured literature search revealed 28 articles reporting comparisons between amblyopia and normal vision control groups for a variety of visual attention tasks. Several of these articles also included neuroimaging measures. A review of these articles suggested that amblyopia does not affect behavioral performance of tasks with a low attentional load, such as cuing tasks, but deficits emerge for tasks with high demands on visual attention such as multiple object tracking. Deficits are not limited to the amblyopic eye but are also evident under fellow eye and binocular viewing conditions suggesting that abnormal early binocular visual experience can fundamentally alter the development of visual attention. Overall, the current literature suggests that amblyopia is associated with reduced visual attention resources. We raise the possibility that this attention resource deficit may be partially associated with an attentional demand for suppression of the amblyopic eye.

Perceptual learning with dichoptic attention tasks improves attentional modulation in V1 and IPS and reduces interocular suppression in human amblyopia

Long-term and chronic visual suppression to the non-preferred eye in early childhood is a key factor in developing amblyopia, as well as a critical barrier to treat amblyopia. To explore the relationship between selective visual attention and amblyopic suppression and its role in the success of amblyopic training, we used EEG source-imaging to show that training human adults with strabismic and anisometropic amblyopia with dichoptic attention tasks improved attentional modulation of neural populations in the primary visual cortex (V1) and intraparietal sulcus (IPS). We also used psychophysics to show that training reduced interocular suppression along with visual acuity and stereoacuity improvements. Importantly, our results revealed that the reduction of interocular suppression by training was significantly correlated with the improvement of selective visual attention in both training-related and -unrelated tasks in the amblyopic eye, relative to the fellow eye. These findings suggest a relation between interocular suppression and selective visual attention bias between eyes in amblyopic vision, and that dichoptic training with high-attention demand tasks in the amblyopic eye might be an effective way to treat amblyopia.

A novel method for utilizing dichoptic attention tasks in amblyopic training

There is converging evidence of attention deficits in individuals with amblyopia. It has been reported that selective visual attention is allocated preferentially toward the non-amblyopic fellow eye in strabismic ambloypes. This attention allocation bias between the eyes is found related to visual suppression in amblyopia. In this study, I introduced a novel method, which uses dichoptic attention tasks to train individuals with amblyopia and has been demonstrated alleviating visual suppression and improving visual functions while reducing interocular attention bias in adults with amblyopia. The method consists of the following components:•

The training tasks include three attention factors (searching, counting and cueing) to implement selective visual attention to the amblyopic eye dichoptically.

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With a dichoptic approach, the targets are presented to the amblyopic eye while the distractors are simultaneously presented to the fellow eye. The tasks are to search and count the targets that are presented to the cued eye among the distractors.

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The training stimuli avoid typical contrast sensitivity-based tasks, and the targets are highly visible allowing them to be seen by the amblyopic eye with poor visual acuity.