Development of the response AC/A ratio over the first year of life

Turner,JE,Horwood,AM,Houston,SM,Riddell,PM. Vision Research 2002, 42(22), 2521-2532

Development of the AC/A ratio over the first year of life

• Mean AC/A ratios do not change over development. Wide variability is typical, so mean responses rarely apply to individuals

This study investigated the development of the link from accommodation to vergence in infants by occluding one eye thus removing binocular cues. Occluded adults continue to converge partially demonstrating that the accommodative drive to vergence (the AC/A link) and proximal cues are sufficient to drive vergence. For infants of all ages, AC/A ratios were found to be in the normal adult range. We conclude that infants can use monocular cues to drive vergence and that this occurs before the age when there is a substantial increase in the accuracy of oculomotor processes. There is flexibility in the developing visual system which is able to produce early vergence responses by relying upon alternative cues.