Attention deficits in Amblyopia

Abstract

Amblyopia is a neuro-developmental abnormality associated with deficits in a broad range of both lowand high-level visual tasks. This is particularly true in strabismic amblyopia where fixation is unstable and there is an increased frequency of microsaccades. In light of the close association between eye movements and attention, we propose a novel hypothesis: that the cost of unstable fixation in amblyopia is a deficit in selective attention. The increased latency for saccades and manual response time with amblyopic-eye viewing is consistent with attention being distracted by unwanted fixational eye movements. We review other attention deficits in amblyopia and discuss whether they are explained by fixation instability, or whether they involve a form of neglect or suppression of the visual input from the amblyopic eye.

Attention in visually typical and amblyopic children

“…Another recent proposal suggests that fixational instability that is especially common in strabismic amblyopic observers produces abnormal selective attention (Verghese et al, 2019). The idea draws from considerable evidence that eye movements and attention are closely linked.…”

Exogenous attention generalizes location transfer of perceptual learning in adults with amblyopia

“…Critically, most have only inferred the role of attention in each of their tasks without directly manipulating it (see [16,17] for more details). More recently, it has been hypothesized that increased fixation instability (particularly for strabismics) leads to higher rates of microsaccades, or fixational eye movements <1°, which results in an amblyopic deficit in selective attention [54]. However, there is controversy as to whether amblyopes reliably generate higher rates of microsaccades (see Discussion of [18]).…”

Neural correlates of visual spatial selective attention are altered at early and late processing stages in human amblyopia

“…Consequently, the brain suppresses the visual information coming from the affected amblyopic eye (interocular suppression), which impairs the fusion of images needed for binocular vision (Bretas & Soriano, 2016). Losses in contrast sensitivity and visual acuity are a landmark of the amblyopic eye (Hess & Howell., 1977;Levi & Harwerth, 1977); however, amblyopic individuals show a range of sensory and oculomotor deficiencies, including higher level deficits (for recent reviews see Kiorpes & Daw, 2018, Levi, 2020Verghese et al, 2019).…”

“…As early as 1962, Van Balen & Henkes suggested that the amblyopic eye was "inattententive", and Singer (1982) pointed to the crucial role of attention in the development of amblyopia and reported that synchronous binocular eye movements are essential for the development of normal visual pathways (Ciuffreda et al, 1979a(Ciuffreda et al, , 1979b. Impaired eye movements, such as poor fixation stability and an increased frequency of microsaccades as observed in human observers with amblyopia have been suggested to not only impact visual perception, but also the spatial allocation of selective attention (Verghese et al, 2019).…”

“…Attentional control can be defined as the ability to focus on task-relevant information and ignore sources of distraction or noise while at the same time constantly monitoring one's environment for new sources of information (Bavelier & Green, 2019). Some studies argue that attentional control is affected in human amblyopia whereas other studies claim that individuals with amblyopia show intact attentional processes especially when attention is guided by a cue to a specific location in the visual field (see Verghese et al, 2019 for a review). Those discrepancies have also been related to differences in characteristics of the stimuli, experimental paradigms and the heterogeneity of the amblyopic population (e.g.…”