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G.M. Tondel, T.R. Candy; Latency of Infants’ Accommodative and Vergence Responses Under Closed–Loop and Open–Loop Conditions . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3148.
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© ARVO (1962-2015); The Authors (2016-present)
A tight relationship between accommodation and vergence permits single, clear percepts in a 3D dynamic environment (an imbalance is known to create binocular anomalies e.g. esotropia). The dynamics of this relationship have not been determined in infancy. The goal of this study was to determine the relative latencies of accommodation and vergence in three viewing conditions: closed–loop, vergence open–loop and accommodation open–loop.
An eccentric videorefractor (PowerRefractor – Multichannel Systems) recorded the binocular refraction and gaze position of infants from 7–20 weeks of age and young adults. Data were collected at 25Hz. Vergence open–loop conditions were created using a longpass filter, which permitted monocular viewing during binocular data collection. Accommodation open–loop conditions were created using a Difference–of–Gaussian stimulus, while vergence was stimulated using a 10 prism diopter base out prism.
Most infants were able to generate accommodation and vergence responses in all conditions, with no significant age trend in response latencies over the age range. Infants’ latencies were significantly longer that adults’ however, although the differences between accommodation and vergence were similar in the 2 groups. In addition, in both age groups, the latency of the open–loop mechanism typically lagged behind the other one. The table below shows the latencies in seconds in each condition for infants and adults.
Infants are able to respond within 2 secs even under open–loop conditions, suggesting that they are able to function relatively maturely in their daily dynamic environment. Of particular note, under open–loop conditions, the time delay between accommodation and vergence is well matched in adults and infants.
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