[The preferential looking technic: material and procedure for testing baby vision]

The preferential looking technique, together with a cover test, retinoscopy and a fundus examination is done in a hospital setting for screening and follow-up of visual deficiencies in infants between 3 and 12 months of age. A series of granting from .375 to 18 cycles per degree are generated by slides, paired with a matched mean luminance uniform area. The child's preferred gaze orientation is determined by an orthoptist unaware of the randomized side of the granting, from a picture of the infant displayed on a closed-circuit television. The baby is gratified after each positive trial. The finest grating toward which the baby systematically orients its gaze is a behavioral estimate of its spatial resolution ability. Binocular and monocular testing are performed in at least 15 minutes. Details of equipment and procedure are described.