Summary: Researchers say children with visual problems such as amblyopia may face developmental issues in brain areas responsible for attention.
Source: University of Waterloo.
A research team has discovered that abnormal vision in childhood can affect the development of higher-level brain areas responsible for things such as attention.
The researchers from the University of Waterloo, University of British Columbia, and the University of Auckland uncovered differences in how the brain processes visual information in patients with various types of lazy eye. In doing so, they are the first to demonstrate that the brain can divert attention away from a lazy eye when both eyes are open.
“Current treatments for lazy eye primarily target the early stages of visual processing within the brain,” said Ben Thompson, a professor in Waterloo’s School of Optometry and Vision Science.”The results from this study show us that new treatments should also target higher-level processes such as attention.”
Lazy eye, known as amblyopia, is a loss of vision that originates in the brain, typically when a child develops an eye turn (strabismic type) or a substantial difference in refractive error between the eyes (anisometropic type). The unequal input causes the brain to ignore information from the weaker eye during brain development. Conventionally, eyecare practitioners treated the different types of lazy eye similarly, primarily because the visual impairments experienced appeared to be the same.
In this study lead researcher, Amy Chow, and her colleagues asked patients to pay attention to a specific set of dots among a group of distracting dots, all moving on a computer screen. However, the tracked dots were only visible in one eye (the weaker eye) while the distracting dots were visible only to the other eye (the stronger eye).
For people with normal vision as well as those with anisometropic amblyopia, showing different images between the two eyes didn’t matter. Both groups were able to overcome the distracting interference and track the dots successfully. Patients with strabismic amblyopia, on the other hand, were unable to direct their attention to the target dots when they were visible to only the weaker eye.
“One of the underlying reasons why some people with lazy eye have poor vision comes down to how the brain suppresses an eye,” said Chow, a PhD student at the School of Optometry and Vision Science at Waterloo. “The poorer-seeing eye is open, the retina is healthy and sending information through to the brain, yet that information does not reach conscious awareness as the brain chooses not to use it.”
About thirty-five thousand Canadians – one per cent of the population – have strabismic amblyopia. The condition can be corrected in childhood, but treatment efficacy can be highly variable. These findings are a stepping stone in developing better treatments of lazy eye.
Funding: The project was supported by the Natural Sciences and Engineering Research Council of Canada.
Source: Ryon Jones – University of Waterloo
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: Open access research for “Dichoptic Attentive Motion Tracking is Biased Toward the Nonamblyopic Eye in Strabismic Amblyopia” by Amy Chow; Deborah Giaschi; and Benjamin Thompson in Investigative Ophthalmology & Visual Science. Published October 2018.
doi:10.1167/iovs.18-25236
[cbtabs][cbtab title=”MLA”]University of Waterloo”Abnormal Vision in Childhood Can Affect Brain Functions.” NeuroscienceNews. NeuroscienceNews, 13 October 2018.
<https://neurosciencenews.com/childhood-vision-brain-function-10015/>.[/cbtab][cbtab title=”APA”]University of Waterloo(2018, October 13). Abnormal Vision in Childhood Can Affect Brain Functions. NeuroscienceNews. Retrieved October 13, 2018 from https://neurosciencenews.com/childhood-vision-brain-function-10015/[/cbtab][cbtab title=”Chicago”]University of Waterloo”Abnormal Vision in Childhood Can Affect Brain Functions.” https://neurosciencenews.com/childhood-vision-brain-function-10015/ (accessed October 13, 2018).[/cbtab][/cbtabs]
Abstract
Dichoptic Attentive Motion Tracking is Biased Toward the Nonamblyopic Eye in Strabismic Amblyopia
Purpose: To determine whether attention is biased toward the nonamblyopic eye under binocular viewing conditions in adults with anisometropic or strabismic amblyopia. We first determined whether attention could be allocated preferentially to one eye in visually normal observers performing a dichoptic attentive motion tracking task. We then assessed dichoptic attentive motion tracking in amblyopia.
Methods: Participants performed a multiple-object tracking task under the following three viewing conditions: target dots to the dominant eye and distractor dots to the nondominant eye (DE condition), vice versa (NDE condition), or all dots to both eyes (binocular condition). Interocular attentional asymmetry scores were computed as the difference in accuracy between DE and NDE conditions. An interocular contrast difference favoring the amblyopic eye was used for all conditions to neutralize amblyopic eye suppression. To test for confounding effects of suppression, participants completed a separate dot enumeration task under dichoptic presentation conditions to obtain an interocular enumeration asymmetry score.
Results: Participants with normal vision demonstrated similar accuracy between the DE and NDE conditions and exhibited slightly impaired performance under dichoptic compared with binocular viewing conditions. Participants with strabismic/mixed amblyopia had significantly higher interocular attentional asymmetry than participants with normal vision or with anisometropic amblyopia, whereby attention was biased toward the nonamblyopic eye. The latter two groups did not exhibit a bias in interocular attention. No interocular asymmetries for the enumeration task were observed for any group.
Conclusions: A nonamblyopic eye bias in the interocular allocation of attention may contribute to the binocular vision impairments caused by strabismic amblyopia.
