December 2010
Volume 10, Issue 15
Free
OSA Fall Vision Meeting Abstract  |   December 2010
Accommodation and vergence responses to hyperopic demands during infancy and childhood
Author Affiliations
  • Erin E. Babinsky
    Indiana University, Bloomington, IN, USA
  • Danielle F. W. Teel
    Indiana University, Bloomington, IN, USA
  • T. Rowan Candy
    Indiana University, Bloomington, IN, USA
Journal of Vision December 2010, Vol.10, 51. doi:10.1167/10.15.51
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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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Abstract

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.

Acknowledgments
Supported by Grants R01 EY014460 (TRC) & P30 EY019008. 
References
Hung, G. K.(1997). Quantitative analysis of the accommodative convergence to accommodation ratio: linear and nonlinear static models. IEEE Trans. Biomed. Eng., 44(4), 306–316.. [CrossRef] [PubMed]
Schor, C. M.(1985). Models of mutual interactions between accommodation and convergence. Am. J. Optom. Physiol. Opt., 62(6), 369–374. [CrossRef] [PubMed]
Westheimer, G.(1963). Amphetamine, barbiturates, and accommodation-convergence. Arch. Ophthalmol., 70, 830–836. [CrossRef] [PubMed]
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