Scotopic optokinetic nystagmus thresholds in 10-week-old infants.

ABSTRACT

PURPOSE: To compare psychophysical and reflexive optokinetic nystagmus (OKN) estimates of dark-adapted scotopic thresholds mediated by the posterior retina in 10-week-old infants and adults. METHODS: A staircase procedure was used to determine the stimulus intensity needed to produce an OKN response to a moving 19 degrees x 19 degrees grating. In the same subjects, a two-alternative, forced-choice procedure was used to obtain thresholds for detecting 10 degrees diameter, 50 ms duration stimuli. RESULTS: Both OKN and psychophysical thresholds of infants are 0.9 log unit higher than those of adults. CONCLUSION: The infant-adult difference in thresholds mediated by retina at the posterior pole is greater than the infant-adult difference in thresholds for full-field stimuli. It is possible that delayed maturation of the posterior retina is the primary determinant of infants' high OKN and psychophysical thresholds.