Improving the effectiveness of the infant contrast sensitivity card procedure.

Based on results from an earlier prototype, custom software and printing techniques were developed to construct a new card-based test of contrast sensitivity (CS) for nonverbal subjects. Compared with the prototype, the new CS card test contains three improvements: (1) larger, more salient test gratings; (2) higher contrast warm-up cards for each spatial frequency set; and (3) smaller contrast step size between adjacent cards. The success of the new cards was evaluated by testing 3.5- and 12-month-old human infants. Results indicated that the new version of the test required little time to complete (mean, 6.5 min) and provided accurate estimates of visual acuity. Also, group contrast sensitivity functions (CSFs) showed substantial development from 3.5 to 12 months of age. Surprisingly, however, group CSFs obtained with the new cards were lower than those obtained with the prototype, a discrepancy that may be due to differences in space average luminance between the two sets of cards. In all, the new CS card procedure possesses several merits that give it potential as an option for assessing spatial vision in infants, toddlers, and subjects with multiple impairments.