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Erin E. Babinsky, Danielle F. W. Teel, T. Rowan Candy; Accommodation and vergence responses to hyperopic demands during infancy and childhood. Journal of Vision 2010;10(15):51. doi: 10.1167/10.15.51.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Accurate accommodation and vergence are required to achieve optimal image quality and single vision. Abnormal visual experience disrupts visual development and therefore accommodation and vergence are central in promoting normal visual development during infancy and childhood. The systems are also neurally coupled and hyperopic children are at risk for over-convergence and strabismus. It is not yet possible to predict which infants will develop this strabismus and the goal of this study was to develop a model to understand the interaction in the coupling. Methods: Several groups have developed related models of accommodation and vergence interactions in adults (Westheimer, 1963; Schor, 1985; Hung, 1997). These models were adapted to examine the developmental implications, incorporating recent data collected from 3-6 month-old infants, 2-4 year-old children, and adults. The model parameters included refractive error, interpupillary distance, and AC/A and CA/C ratios. Results: For a target at a 50 cm viewing distance, simulations of refractive errors indicated that hyperopic refractive errors ≧6D resulted in at least a 4D (or MA) conflict between the accommodation and vergence responses for all age groups, while varying the AC/A ratio suggested that high values (1.0 MA/D for the infants, 1.2 MA/D for the preschoolers) resulted in >2D of conflict between the vergence and accommodation systems. Varying the CA/C ratio induced less conflict, but simulations with larger ratios (≧1.4 D/MA) did take longer to stabilize. Conclusions: The simulations highlight the role of the AC/A ratio in oculomotor processing during development and demonstrate the potential strategies that hyperopic individuals could adopt.
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