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Erin Babinsky, Vidhyapriya Sreenivasan, T. Rowan Candy; The role of heterophoria and its adaptation in typically developing children. Journal of Vision 2013;13(9):729. doi: 10.1167/13.9.729.
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© ARVO (1962-2015); The Authors (2016-present)
Visual experience during postnatal development is dependent on the accommodative and vergence systems, in controlling retinal image quality and correspondence. How young children’s oculomotor systems coordinate these responses in the presence of hyperopic refractive error and a narrow interpupillary distance is poorly understood, and is central in understanding refractive strabismus. One key problem is how the systems compensate for additional convergence driven by coupled accommodation overcoming their hyperopia. METHODS: Eye alignment was recorded using Purkinje image eye tracking at 25Hz, while subjects viewed naturalistic targets monocularly for one minute and then binocularly for 5s, at 33cms. The dissociated heterophoria was derived from these data as a representation of resting alignment of the eyes. The protocol was then repeated to test adaptation with the binocular phase lengthened to 60s with 10 prism diopters (pd) of base out prism (increasing the vergence demand). Subjects were typically-developing children aged 2-10 years (n = 49) and adults (n = 16), who also underwent a clinical eye examination. RESULTS: While the presence of uncorrected hyperopia (mean +0.92D, SD 1.1D) in the children suggests they should have a convergent eye alignment in dissociated conditions, 73% had a divergent eye alignment (exophoria <-2pd) for the 33cm viewing distance, as compared to 81% in adults. The mean heterophoria was -4.0pd (SD 4.6) in children and -7.1pd (SD 5.3) in adults (p = .02). At the end of the adaptation period, the children’s mean heterophoria was 2.2pd (p = .002) more convergent than their baseline phoria and took 40s to return to baseline value. Despite the presence of hyperopia, these young children typically are exophoric for this near viewing distance. Their apparent ability to adapt suggests that this misalignment may be desirable.
Meeting abstract presented at VSS 2013
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