The early phase of dark adaptation in human infants

Two types of thresholds with 8 degrees circular test fields were measured in 7- and 13-week-old human infants and in adults. Increment thresholds were measured against adapting fields of 0.50 and 50 cd/m2. All ages showed Weber's Law for incremental sensitivity over this 2 log unit range of luminance. Thresholds during early dark adaptation were also measured for the 5 sec immediately following the offsets of these adapting fields. The reductions in threshold during the early phase of dark adaptation were quantitatively similar in all age groups at both adapting luminances, despite substantial developmental differences in the absolute values of these thresholds. These data do not reject the hypothesis that the neural processes underlying early dark adaptation are adult-like in early infancy.