Developmental changes in the balance of disparity, blur and looming/proximity cues to drive ocular alignment and focus
Horwood, A, Riddell P. Perception 2013, 42, 693-715 doi:10.1068/p7506
- Proximal /looming cues are important for driving accommodation and convergence in infants less than 14 weeks of age, but then decline dramatically, while binocular disparity becomes increasingly important in later childhood. Infants from 14-26 weeks are able to use blur, proximal and disparity cues equally.
Accurate coordination of accommodation and convergence is necessary to view near objects and develop fine motor coordination. We used a remote haploscopic videorefraction paradigm
to measure longitudinal changes in simultaneous ocular accommodation and vergence to targets at different depths, and to all combinations of blur, binocular disparity, and change-in-size (‘proximity’) cues. Infants were followed longitudinally and compared with older children and young adults, with the prediction that sensitivity to different cues would change during development. Mean infant responses to the most naturalistic condition were similar to those of adults from 6–7 weeks (accommodation) and 8–9 weeks (vergence).
Proximity cues influenced responses most in infants of less than 14 weeks of age, but sensitivity declined thereafter. Between 12 and 28 weeks of age infants were equally responsive to all three cues, while in older children and adults manipulation of disparity resulted in the greatest changes in response. Despite rapid development of visual acuity (thus increasing availability of blur cues), responses to blur were stable throughout development. Our results suggest that, during much of infancy, vergence and accommodation responses are not dependent on the development of specific depth cues, but make use of any cues available to drive appropriate changes in response.