The contrast sensitivity of the newborn human infant.

PURPOSE

To measure the binocular contrast sensitivity (CS) of newborn infants using a fixation-and-following card procedure.

METHODS

The CS of 119 healthy newborn infants was measured using stimuli printed on cards under the descending method of limits (93 infants) and randomized/masked designs (26 infants). One experienced and one novice adult observer tested the infants using vertical square-wave gratings (0.06 and 0.10 cyc/deg; 20/10,000 and 20/6000 nominal Snellen equivalent); the experienced observer also tested using horizontal gratings (0.10 cyc/deg) and using the Method of Constant Stimuli while being kept unaware of the stimulus values.

RESULTS

The CS of the newborn infant was 2.0 (contrast threshold = 0.497; 95% confidence interval: 0.475-0.524) for vertically oriented gratings and 1.74 (threshold = 0.575; 95% confidence interval: 0.523-0.633) for horizontally oriented gratings (P < 0.0006). The standard deviation of infant CS was comparable to that obtained by others on adults using the Pelli-Robson chart. The two observers showed similar practice effects. Randomization of stimulus order and masking of the adult observer had no effect on CS.

CONCLUSIONS

The CS of individual newborn human infants can be measured using a fixation-and-following card procedure.