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Eric Seemiller, Jingyun Wang, T. Rowan Candy; The sensitivity of vergence eye movements in young infants. Journal of Vision 2014;14(15):61. doi: 10.1167/14.15.61.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: The fine accuracy of vergence eye movements in human adults is driven predominately by retinal disparity, with influence from several other factors. Prior to the apparent onset of sensitivity to disparity between 3–5 months of age, young infants are capable of making disconjugate eye movements toward a disparate target, albeit inaccurately (Aslin 1977). Here, we present a dynamic, full-cue vergence stimulus to five- to eight-week-old infants to determine the sensitivity of their eye movements to change in stimulus position. Methods: Adults and infants viewed a movie with a naturalistic amplitude spectrum presented on a screen mounted on a motorized track. The stimulus was moved sinusoidally in space over three amplitudes (0.5, 0.25 and 0.125 MA). A photorefractor on axis with the stimulus captured the position of the first Purkinje images at 25 Hz. An FFT was used to determine the frequency content of the vergence response to the stimulus. The signal-to-noise ratio (SNR) at the desired stimulus frequency was computed from the adjacent frequencies and also in comparison with responses to a static target. Results: The mean SNRs decreased as a function of stimulus amplitude in all age groups. Responses were present but weakest for the youngest infants (means= 3.51, 2.22, 1.25) compared to 3 month olds (means=6.18, 3.12, 1.98) and adults (means= 9.71, 8.83, 4.64). This suggests that the youngest infants studied are capable of vergence modulation to high amplitude stimuli and also that their vergence responses are potentially less sensitive than found in older infants and adults.
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