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Eric Seemiller, Nicholas Port, T. Candy; The Stability of Fixation in Depth in 5-10-Week-Old Infants. Journal of Vision 2016;16(12):203. doi: 10.1167/16.12.203.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction Though studies have found that instability in horizontal and vertical eye position may limit visual processes in strabismic and amblyopic observers (e.g., Subramian, et al. 2013), little attention has been paid to fixation in depth. Could instability in binocular alignment be a significant barrier to disparity processing in young infants? In this study, observers were presented with random noise while variation in their horizontal, vertical and disconjugate eye position over time was determined. Methods Adults (n=9) and infants (n=11) aged between 5 and 10 weeks viewed dichoptic, random noise (60° by 44°) from a viewing distance of 65 cm. Each noise pixel subtended 6° vertically by 3° horizontally, and updated at 3 Hz to prevent prolonged binocular fixation on a feature. The only information for alignment in depth came from the zero-disparity binocular cue. Saccades > 2° were removed and intersaccade intervals were normalized. Five-second epochs of cooperative fixation within the central 10 degrees of the stimulus were analyzed. Results & Discussion For adults, the standard deviation (SD) of horizontal vergence position was smaller during binocular viewing (mean +/- SD = 0.197 +/- 0.077°) than monocular viewing (0.259 +/- 0.216°; paired t-test, p =0.036). Infants (0.391 +/- 0.533°) had larger standard deviations in binocular viewing than adults by a factor of two. Interestingly, vertical vergence position in infants (0.232 +/- 0.33°) was not significantly different from adults (0.279 +/- 0.251°). Longitudinal data from four infants revealed that SD in horizontal vergence decreased by an average of 0.345 +/- 0.319° between 5 and 10 weeks. These data suggest immaturity in horizontal vergence that may not be present in vertical vergence between 5 and 10 weeks. Implications for normal and abnormal binocular development will be discussed.
Meeting abstract presented at VSS 2016
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