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Sonisha Neupane, Vidhyapriya Sreenivasan, Yifei Wu, Celina Fraire, Katie Connolly, Elizabeth Murray, Don Lyon, T Rowan Candy; The conflict between accommodation and vergence demands during human early childhood. Journal of Vision 2019;19(8):44. doi: https://doi.org/10.1167/19.8.44.
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Purpose: Infants are typically hyperopic with a narrower inter-pupillary distance than adults. To achieve focused and aligned retinal images to promote typical visual development a young child must accommodate more than a typical adult while generating less vergence. This puts their two motor systems in apparent conflict relative to a typical adult. We made simultaneous recordings of accommodation and vergence performance of young children to determine the extent to which their accommodation and vergence systems could overcome their motor demands.
Methods: Simultaneous Purkinje image tracking and eccentric photorefraction (PlusOptix PowerRef 3) were used to record eye alignment and refractive state of age-matched non-strabismic hyperopic and emmetropic children with no optical correction (N=32, Mean Age: 4.66 years). Subjects viewed naturalistic images at 80 & 33cm distances in monocular and binocular viewing. Some of the hyperopes then received optical correction from their clinician.
Results: The emmetropes exhibited typical relationships between accommodation and vergence at these distances in binocular conditions (Change: A=1.97±0.84D, V=1.68±0.67 MA). The hyperopes exhibited a range of behaviors. On average they were similar to the emmetropes even in the absence of optical correction (Change: A=1.97±0.76D, V=1.81±0.3 MA). The hyperopes who were prescribed optical correction exhibited relatively minimal changes in phoria despite their change in accommodative effort.
Conclusion: Simultaneous measures of accommodation and vergence provide critical information about the conflict between coupled vergence and accommodation responses in hyperopes. The data suggest these individuals can display an unexpected range of behaviors from fully typical to decompensated convergent deviation.
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