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Accommodation and vergence latencies in human infants
Grazyna M Tondel1, T Rowan Candy
1Indiana University School of Optometry, 800 E. Atwater Avenue, Bloomington, IN 47405, USA.
Insights
Infants as young as 7 weeks show adult-like visual coordination. Accommodation and vergence latencies correlate, suggesting linked development in early postnatal vision.
Area of Science:
- Developmental neuroscience
- Ophthalmology
- Visual processing
Background:
- Simultaneous single and clear vision during postnatal development relies on accurate and temporally coordinated accommodation and vergence.
- Understanding the dynamic interplay, specifically response latencies, is crucial for assessing visual system maturation.
Purpose of the Study:
- To investigate the latencies of accommodation and vergence responses in infants and adults.
- To examine the relationship between accommodation and vergence latencies during early postnatal development.
Main Methods:
- Tested infants and adults under three conditions: binocular closed-loop, vergence open-loop, and accommodation open-loop.
- Stimuli included a moving target in depth and a prism-induced disparity step change.
- Measured response latencies for accommodation and vergence.
Main Results:
- A significant correlation between accommodation and vergence latencies was observed in infants (7-23 weeks) under binocular conditions.
- Some infants exhibited adult-like latencies (<0.5 s) as early as 7-8 weeks.
- Latencies were generally under 2 s across the infant age range, with shorter responses in stimulated versus open-loop conditions.
Conclusions:
- Many infants aged 7-23 weeks demonstrate rapid accommodation and vergence responses (<1 s) in binocular closed-loop settings.
- The correlated latencies suggest that common factors limit both accommodation and vergence systems from early infancy.
Purpose:
Achieving simultaneous single and clear visual experience during postnatal development depends on the temporal relationship between accommodation and vergence, in addition to their accuracies. This study was designed to examine one component of the dynamic relationship, the latencies of the responses.
Methods:
Infants and adults were tested in three conditions (i) binocular viewing of a target moving in depth at 5 cm/s (closed loop) (ii) monocular viewing of the same target (vergence open loop) (iii) binocular viewing of a low spatial frequency Difference of Gaussian target during a prism induced step change in retinal disparity (accommodation open loop).
Results:
There was a significant correlation between accommodation and vergence latencies in binocular conditions for infants from 7 to 23 weeks of age. Some of the infants, as young as 7 or 8 weeks, generated adult-like latencies of less than 0.5 s. Latencies in the vergence open loop and accommodation open loop conditions tended to be shorter for the stimulated system than the open loop system in both cases, and all latencies were typically less than 2 s across the infant age range.
Conclusions:
Many infants between 7 and 23 weeks of age were able to generate accommodation and vergence responses with latencies of less than a second in full binocular closed loop conditions. The correlation between the latencies in the two systems suggests that they are limited by related factors from the earliest ages tested.
