Growth Curve for Infant's "Fixation To Light" Using Gaze Reaction Time

The purpose of this study was to investigate the developmental pattern of infant's gaze initiation time (reaction time) as a function of age. To fit a growth curve model to this function, we hypothesized that reaction time would reduce with age.

A cross-sectional study was conducted. Six hundred ninety-four (694) healthy infants (age = 3-8 months) participated. Infant's gaze reaction time to light stimuli was measured using Baby Vision Screener (BaViS). The BaViS is a dome-shaped device that presents LED stimuli. Infants were tested while in a supine position under this dome in a dark room. The examiner presented the LED stimuli and monitored and recorded the infant's gaze response using a real-time video feed. reaction time was obtained through semi-automated video processing. reaction time was modeled as a function of age using the Box-Cox power exponential generalized additive model for location, scale, and shape (GAMLSS) to generate a growth curve.

Reaction time was quantifiable in 682 infants. reaction time significantly (P < 0.001) reduced with age (e.g. 3-month-old infants had a median reaction time of 684 ms [P25 and P75 = 548 and 846 ms] whereas 8-month-old infants had 397 ms [350 ms and 457 ms] in the upper visual field). The reaction time distribution in the growth curve was wider for younger infants than for older infants (e.g. the reaction time range between the 5th and the 95th percentile was 925 ms for 3-month-old and 385 ms for 8-month-old infants).

As hypothesized, a developmental trend for gaze response was observed. The reduction in variability of this behavioral measure with age could be indicative of neural maturation. The percentile growth curve of reaction time obtained from this behavioral study can be explored further as a quantitative clinical measure for evaluating infant vision.