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Kimberly Meier, Deborah Giaschi, Laurie Wilcox, Eric Seemiller, T. Candy; Vergence responses to fine and coarse disparities: Adult-like tuning functions at 5 years of age. Journal of Vision 2016;16(12):841. doi: 10.1167/16.12.841.
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© 2017 Association for Research in Vision and Ophthalmology.
Depth information can be extracted from small retinal disparities (fine stereopsis), or large disparities that give rise to diplopia (coarse stereopsis). Coarse stereopsis may mature early in life and be crucial for calibrating binocular pathways during development. This suggestion is consistent with previous work showing adult-like depth discrimination at 4 years of age for diplopic disparities, but not until 13 years for fused disparities (Giaschi et al., 2013). In the current study we used a new paradigm to assess disparity sensitivity in children using eye-tracking. Vergence eye movements were recorded in 10 adults and 10 five-year-olds with typical vision. Dichoptically-presented images were viewed through polarized lenses. During each of 260 trials, a cartoon character (2.2 deg wide) was presented in the plane of the screen for 1500 ms, stepped to a crossed or uncrossed disparity (0, 0.5, 1, 2, 4, 8, 16 deg) for 320 ms, and followed by a blank screen for 680 ms. Diplopia was then assessed by having participants report whether they perceived 1 or 2 characters at each disparity (in random sequence). Children and adults showed the same peak vergence amplitudes across the disparity range (p > .05). These tuning functions demonstrated increased amplitude as a function of disparity until ±2 deg, corresponding to the fine disparity range. Coarse disparities yielded vergence eye movements with reduced peak amplitudes, but in the expected direction in depth. This reduction of vergence amplitudes occurred over the range of disparities that appeared diplopic. Our results confirm that fine and coarse disparities can drive vergence eye movements, show that this aspect of binocular function is adult-like at age 5 and reveal an interesting relationship between vergence amplitudes and depth perception. This paradigm may be useful with children too young for psychophysical testing, potentially providing valuable insights into binocular visual development.
Meeting abstract presented at VSS 2016
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