Visual acuity of human infants at scotopic, mesopic and photopic luminances.

Visual acuity of 2-month-old infants and adults was measured between -2.6 and +2.7 log10 cd/m2 using standard psychophysical techniques. The acuity-vs-luminance curve was similar for infants and adults: acuity improved with increasing luminance until 0.0 log cd/m2, and was constant above that luminance. However, the infant curve was slightly shallower than the adult curve, and infant acuity was over 3.5 octaves poorer than adult acuity at all luminances. The infant acuity-vs-luminance curve was compared with adult curves measured 21 degrees and 51 degrees from fixation, and at 21 degrees with +8, +/- 3.25 and 0.0 D of experimental refractive error. The results indicated that infants' poor acuity cannot be fully explained by: refractive error, foveal immaturity, scotopic detection of stimuli, functional similarity between infant vision and adult vision in the periphery, or by an overall reduction in visual sensitivity.