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Erin Babinsky, Tawna Roberts, Eric Seemiller, T. Rowan Candy; Accommodation and vergence: comparing 3-month-old infant responses to oculomotor model performance. Journal of Vision 2012;12(9):478. doi: 10.1167/12.9.478.
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© ARVO (1962-2015); The Authors (2016-present)
Oculomotor models have been developed over the past 50 years to understand the systems controlling vergence and accommodation in adult humans. The elements of these models (e.g. phasic and tonic components, plant, and cross-links) have been developed to model adult empirical behavior, but their relevance to performance during infancy is to be determined. Infant accommodation and vergence responses were measured in a full-cue binocular condition, an open-loop accommodation condition (CA/C ratio), and an open-loop vergence condition (AC/A ratio). Three-month-old infants (n = 10) watched an animated movie that was moved between dioptric positions of 1.1D and 2.85D. Responses were recorded with the PowerRefractor (Multi Channel Systems) at 25Hz. The mean change in accommodation and vergence responses was calculated for each condition. Mean amplitudes in the binocular condition for accommodation and vergence were 2.27 D and 1.57 MA. Mean CA/C and AC/A ratios for these infants were 1.63 D/MA and 0.53 MA/D. These empirical values were compared to simulations using Hung and Semmlow’s static model (1980) and Schor’s dynamic model (1992). The response ratios predicted by the adult parameters in each model underestimated the empirical CA/C in infants (<0.80 D/MA) and overestimated the empirical AC/A ratio in infants (>0.85 MA/D). Individual infant full cue, and open-loop empirical data could be simulated with a single set of adjusted parameters to generate mean amplitudes of 1.89 D and 1.40 MA and ratios of 1.50 D/MA and 0.62 MA/D while incorporating the individual’s refractive error in addition (no significant differences were found between the two models). These models only marginally underestimated the empirical accommodation and vergence amplitudes, and the incorporated parameters are sufficient to capture the critical immaturities of the human infant.
Meeting abstract presented at VSS 2012
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