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Rowan Candy, Grazyna Tondel; Human infants' tracking of dynamic accommodative stimuli. Journal of Vision 2004;4(11):46. doi: 10.1167/4.11.46.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Human infants are typically born with a hyperopic refractive error. They must accommodate to bring objects at close viewing distances into focus. Previous studies of accommodative performance in infants suggest that they accommodate inaccurately to static targets for a number of months after birth. The goal of this study was to characterise infants' ability to track dynamic accommodative stimuli, with a view to defining retinal image quality as infants experience their habitually dynamic environment.
Methods: Accommodative responses were recorded at 25Hz to targets moving at three velocities (5, 20 & 50 cm/s), between 20 and 50cm viewing distances. Eccentric photorefraction was used to record refraction and gaze position from both eyes simultaneously.
Results: Infants (8 to 18 weeks of age) were able to generate dynamic accommodative responses in the direction of the target motion. The latency of infant responses was often less than one second and they demonstrated the ability to modify the velocity of their response to correlate with the stimulus velocity.
Conclusions: By approximately 3 months, human infants are able to both interpret the velocity of a dynamic accommodative stimulus, and initiate a response within 1s. This implies the capacity to rapidly explore the 3-dimensional nature of their environment, and the potential for a typically well-focussed foveal retinal image.
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