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T. Rowan Candy, Erin Babinsky, Tawna Roberts, Eric Seemiller; The Correlation Between Accommodation and Vergence Responses in Three-Month-Old Human Infants. Journal of Vision 2012;12(9):791. doi: 10.1167/12.9.791.
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Purpose: Classical models of accommodation and vergence incorporate a number of components either in the context of the Maddox/Heath classifications (blur-driven, disparity-driven, tonic, coupled, proximal and voluntary) or Controls Theory models (phasic, tonic, coupling and plant). In either vocabulary, these components may combine with different weights to generate relatively coupled or independent motor responses. Infants have increased accommodative demands relative to adults (hyperopia) yet reduced vergence demands (narrow IPD) and therefore less effective coupling in the final motor response might be advantageous during development. Methods: This reasoning was tested by recording accommodation and vergence responses simultaneously from 74 3-4 month-old infants using an eccentric photorefractor (Multi Channel Systems, 25Hz). The infants were presented with an animated movie (a broadband spatial amplitude spectrum) moving repeatedly in a ramp fashion between dioptric distances of 1.1 and 2.85D. The subjects viewed the movie in full-cue binocular viewing conditions. The correlation between the accommodation and vergence responses to this stimulus was determined. Results: Sixty-six infants gave usable data and thirty-seven of them had a correlation between their accommodation and vergence data of greater than 0.6. The vergence responses were more repeatable within individuals than accommodation and relative drift of the accommodation response was not uncommon at levels (on the order of 1-2 D) beyond the depth of focus predicted by their expected acuity. Conclusions: These data suggest that while the accommodation and vergence systems demonstrate coupled responses during early infancy, the effective coupling in full-cue conditions is not complete. While this may lead to inaccurate responses at times, it could also permit young infants to maintain both focused and aligned visual experience during early development and reduce the potential for strabismus.
Meeting abstract presented at VSS 2012
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