Abstract
This research was prospectively designed to determine whether the contrast sensitivity function of the newborn infant was low-pass or bandpass, and whether contrast sensitivity could be accurately measured using an 0.083 cy/deg (20/7200) square-wave stimulus. The results were retrospectively analyzed to determine whether our two data-collection protocols—the Method of Constant Stimuli (MCS) and the descending Method of Limits (dLIM)—yielded similar results. Methods: Infant visual performance was measured using a card-based fixation-and-following technique and a yes-no psychophysical paradigm. In across-subjects experimental designs, a pilot study used MCS (N=47 visual acuity; N=40 contrast sensitivity at 0.083 cy/deg), and a main experiment used dLIM (N=22 visual acuity; N=21 contrast sensitivity at 0.083 cy/deg; N=21 at 0.301 cy/deg), to measure the visual performance of healthy newborn infants in a hospital postpartum unit. Two low-pass and one bandpass contrast sensitivity functions estimated the peak neonatal contrast sensitivity. Psychometric functions from the MCS and dLIM data sets were compared while taking the stimulus presentation protocols into account. Results: In the main experiment, the bandpass contrast sensitivity function fit the data best. However, the 0.083 cy/deg square wave stimulus underestimated the best performance of newborn infants by only 0.15 log10 units or less for all three candidate contrast sensitivity functions. MCS produced numerically slightly higher sensitivity, but MCS and dLIM data agreed closely when analyzed to take the stimulus presentation contingencies into account. The MCS and dLIM results are more similar when larger between-stimulus step sizes are used. Conclusions: The contrast sensitivity function of the newborn infant is bandpass. Newborn contrast sensitivity is well measured using a 0.083 cy/deg square wave target, regardless of which contrast sensitivity function is correct. MCS and dLIM yield wholly comparable results, with no evidence of influence from other factors such as infant inattention or examiner impatience.
Meeting abstract presented at VSS 2018