Preferential Looking (PL) Test

The Preferential Looking test is used to assess visual acuity in infants and young children who are unable to identify pictures or letters. The child is presented with two stimulus fields, one with stripes and the other with a homogeneous gray area of the same average luminance as the striped field. The location of the stripes is randomly alternated. Typically, infants and children will look at the more interesting stripes (if they can detect them) rather than at the blank field.

During the test, the child will sit on an adult's lap facing forward. On the card, a small peephole is centered between the two fields. An observer views the child through the peephole and judges the location of the stripes based on the child's head and eye movements.

If the child can see the stripes, he/she will prefer to look at them. If the child cannot see them, the striped field will look the same as the blank gray field, and the child will not show a preference. The smallest stripe width for which the observer can consistently identify the location of the stripes is considered to be the child's resolution threshold (visual acuity).

A subject completing the Preferential Looking test.