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Binocularity in infancy
1Department of Psychology, University College London, UK.
Insights
Infant binocular vision emerges around 10-16 weeks, with sensitivity to disparity and stereoacuity rapidly improving. This development occurs independently of eye alignment and can adapt even with strabismus.
Area of Science:
- Developmental neuroscience
- Ophthalmology
- Visual processing
Background:
- Functional binocular interaction in the human visual cortex typically begins between 10 and 16 weeks of age.
- Measures of sensitivity to binocular correlation and disparity show consistent onset timing.
- Behavioral and visual evoked potential (VEP) measures in infants demonstrate a narrow 2-week range for the onset of binocularity.
Purpose of the Study:
- To investigate the timeline and characteristics of early binocular vision development in infants.
- To explore the relationship between binocularity onset, eye alignment, and strabismus.
- To understand the plasticity and adaptability of binocular visual pathways in early childhood.
Main Methods:
- Utilized behavioral assessments to measure sensitivity to binocular correlation and disparity.
- Employed electrophysiological techniques, specifically visual evoked potentials (VEP), to determine the onset of binocularity.
- Observed infants with and without strabismus to assess the impact on binocular development.
Main Results:
- Infant binocularity onset is consistently observed between 10 and 16 weeks of age.
- Post-onset, sensitivity to disparity and stereoacuity increase rapidly.
- Binocular development proceeds even with strabismus and is not solely dependent on eye alignment.
Conclusions:
- The onset of binocular vision is a distinct developmental event in early infancy.
- Binocular visual pathways exhibit significant plasticity, adapting to conditions like strabismus.
- Further research is needed to understand pre-binocular visual system organization and the neural basis of developing disparity processing.
Abstract:
A variety of behavioural and electrophysiological studies agree that the onset of functional binocular interaction in human visual cortex normally occurs between 10 and 16 weeks of age. Measures of sensitivity to binocular correlation and to disparity agree closely, and behavioural and visual evoked potential measures on the same infant show onset of binocularity within about a 2 week range. Beyond the initial onset, the maximum disparity to which infants are sensitive increases steadily and stereoacuity is found to increase very rapidly. The initial development of binocularity does not appear to be a consequence of improving alignment of the eyes and occurs even in the presence of strabismus. However, the connections subserving binocularity are plastic in early childhood; they can be disrupted by unilateral strabismus, although in some strabismic children who use both eyes for fixation, they can adapt to serve stereo function at the angle of deviation and re-adapt, albeit temporarily, to the surgical alignment of the eyes. These findings allow us to pose some as yet unanswered questions about the development of binocularity, including: How is the infant's visual system organised before the establishment of binocularity? How does the pre-binocular infant maintain vergence? And what neural changes underlie the increase in performance for small and large disparities following the initial onset of binocular function?