Purchase this article with an account.
GM Tondel, J Wang, TR Candy; Infants' Ability To Track Ramp Accommodative Stimuli . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4708.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Human infants' responses to static accommodative blur have been studied previously. Accommodative accuracy matures during the first 6 months. The purpose of this study was to investigate infants' sensitivity and responses to dynamic blur, by presenting a dioptrically ramped stimulus. Methods: An eccentric videorefractor (PowerRefractor - Multichannel Systems) was used to sample accommodative responses of 1 to 9 month-olds and adults. Measurements were taken at a frequency of 25Hz while targets were smoothly ramped over 3 seconds between viewing distances of 1m and 25cm, corresponding to a dynamic stimulus of 1D/sec. Results: All infants older than 3 months of age detected and smoothly tracked the target in both directions, from a demand of 1 to 4D, and from 4 to 1D. The standard deviation of the responses at 1m and 25cm were less than 1/4 of the amplitude of the change in response as the target moved from one distance to the other. The smooth monotonic tracking response was of the same duration as in adults, and was not a single ballistic movement - stopping the target at intervening distances halted the response (at 50cm and 33cm). Most infants younger than 3 months were also able to change their focus in response to the 3D change in demand. Conclusion: Young infants (at least after 3 months) have the motor and sensory capacities to generate a smooth continuous accommodative response to a ramp stimulus moving at 1D/sec. This suggests that once accommodation starts to change during a trial, dynamic blur discrimination and the latency of the motor response do not limit performance.
This PDF is available to Subscribers Only