Preferential looking as a measure of visual resolution in infants and toddlers: a comparison of psychophysical methods.

We used preferential looking to estimate the monocular visual resolution of children 6-36 months old and compared results from 3 psychophysical methods: Taylor and Creelman's PEST staircase, our modification of the PEST procedure, and the method-of-constant stimuli. Estimates of visual resolution for 48 children tested with the original and modified PEST procedures and for 50 children tested with the method-of-constant stimuli and the modified PEST procedure showed excellent agreement across procedures, with the modified PEST procedure requiring the fewest trials and the least time. Results from the modified PEST procedure for 168 children with normal eye alignment and minimal refractive errors indicated that monocular visual resolution improves from 6.5 min at 6 months to 1.2 min at 36 months. Preferential looking combined with the shortened PEST procedure should be useful for testing the visual resolution of preverbal children with eye problems.