Contrast sensitivity in infants and children with Down syndrome.

A new contrast sensitivity (CS) card test was used to estimate contrast sensitivity in 18 infants and children with Down syndrome (DS). The results showed that although the overall shape of the contrast sensitivity functions (CSFs) of the subjects with DS was the typical inverted-U, their CSFs were depressed in comparison to control subjects and this relative loss became larger with increasing spatial frequency. In addition, there was little improvement in CS with age and the mean CSF among children with DS (mean age = 7.3 years) was equivalent statistically to a group of 12-month-olds without DS. The Teller Acuity Cards (TAC) were also used to assess visual acuity in 17 of the 18 children in our sample. The results of these tests showed that their visual acuity (VA) was significantly lower than normal, but was consistent with that extrapolated from each subject's CSF. Taken together with previous anatomical and developmental findings, our results suggest that the deficits in spatial vision among children with DS is due primarily to restricted cortical development, and secondarily, to the additional accommodative and ocular conditions that are prevalent in this population.