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Yifei Wu, Vidhyapriya Sreenivasan, Erin Babinsky, T. Rowan Candy; Vergence adaptation in young children. Journal of Vision 2014;14(15):71. doi: https://doi.org/10.1167/14.15.71.
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© ARVO (1962-2015); The Authors (2016-present)
Young children have decreased convergence and increased accommodation demands relative to adults, resulting from their reduced interpupillary distance and typically hyperopic refraction. Accommodation focuses the retinal image and generates accommodative convergence through neural coupling. Excessive accommodative convergence is implicated in refractive esotropia in hyperopes. Adults show adaptation in their vergence responses. Do typical young children also show adaptation? We tested this hypothesis by measuring heterophoria adaptation in children. METHODS Eccentric photorefraction and Purkinje image tracking (MCS PowerRefractor, 25Hz) were used to record accommodation and eye alignment in adults and children 3.25 - 5 years of age. Participants viewed a naturalistic target at 80 cm binocularly for 15 secs and then monocularly for 15 secs. Each heterophoria measurement was derived from the difference between these two alignments. After baseline heterophoria was measured, additional vergence demand was introduced using prism placed before one eye and heterophoria measurements were continued. Recovery was then tracked after removal of the prism. RESULTS 86% of young subjects maintained fusion during 6pd extra vergence demand and adapted to, on average, 55% of the additional demand (range 38% - 67%). 90% of adults demonstrated similar responses with 10pd extra demand and showed adaptation of 52% (range 39% - 72%). Henson and North (1980) reported adults showing average adaptation of 72% with 6pd. CONCLUSION Children from 3.25 - 5 years and adults exhibited heterophoria adaptation for an 80cm target and demonstrated recovery to baseline. In typically developing hyperopic children, this adaptation might have protective effects against esotropia.
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