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T. Rowan Candy, Eric Seemiller, Colin Downey, Lawrence Cormack; Infants' Dynamic Accommodation and Vergence Tracking of an Unpredictable Stimulus. Journal of Vision 2016;16(12):61. doi: 10.1167/16.12.61.
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© ARVO (1962-2015); The Authors (2016-present)
Typical development of the binocular visual system requires focused and aligned retinal images. These image attributes are defined by accommodation and vergence motor responses in the habitual environment. We have shown that these motor responses are sensitive to less than 0.50 D or MA of target movement by 3 months of age in human infants (Wang & Candy, 2010; Seemiller et al., 2015). The purpose of this study was to move from spatial sensitivity into addressing the temporal characteristics of these systems in early infancy, using an eye movement correlogram approach (Mulligan et al., 2013). Infants and adults were presented with a stimulus moving randomly in depth on a motorized track. The target was a cartoon movie with naturalistic spatial amplitude spectra, moving randomly over distances between 33 and 80cm from the participant. Eye position and refractive state were recorded binocularly and simultaneously at 50Hz using eccentric photorefraction and purkinje-image tracking analyses of video images (PowerRefractor, PlusOptix). Functionally emmetropic adults and typically developing infants aged from 8 to 17 weeks watched these stimuli for 20 and 45s trials. The time series of the responses and their cross-correlograms with the stimulus were then examined. Adult responses were consistent with the literature; both vergence and accommodation were tightly coupled with the stimulus and with each other. Infant vergence responses tended to be more robust than their simultaneously recorded accommodation responses for these unpredictable dynamic stimuli and viewing distances. Vergence responses were more variable than in adults, while accommodation was more variable still, and often seemingly uncoupled from vergence. These data suggest that the vergence system is more responsive than the accommodation system during the first months of postnatal development, and that accommodative convergence is not the primary drive to vergence in this period.
Meeting abstract presented at VSS 2016
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