Stereopsis testing in 18- to 35-month-old children using operant preferential looking.

Forced choice operant preferential looking (OPL) was used to evaluate stereopsis in children between 18 and 35 months of age. Eighty-three children who passed a vision screening were tested with a ring-shaped random dot target that stood out in depth. Food was used to reinforce looking at the target. Children were also administered the Random Dot E (RDE) as a comparison measure. Four children were unable to complete testing with OPL compared with 31 who were unable to complete testing with the RDE. This difference was most apparent in children under 24 months of age. This new procedure appears to be a useful technique to evaluate stereopsis in very young children.