Testability of preschoolers on stereotests used to screen vision disorders.

OBJECTIVE: The purpose was to determine whether preschool children aged 3 years 0 months through 3 years 6 months could be tested with the Random Dot E, Stereo Smile, and Randot Preschool stereoacuity tests, which are random dot stereotests marketed for use with preschoolers.
METHODS: A total of 118 children from five Vision In Preschoolers Study Clinical Centers participated. Strabismic children, as determined by the cover test at distance and near, were excluded from this study. Stereopsis was tested on each child using each of the three tests in a variable, balanced order. A child's testability for each test was determined by the ability to complete the nonstereo task (pretest) and the gross stereo task for each stereotest. Proportions of children able to perform each test were compared using statistical methods accommodating multiple measurements per child.
RESULTS: Testability of children on the pretest was greater for the Stereo Smile test (91%) than for the Random Dot E test (81%; p = 0.007) or the Randot Preschool test (71%; p < 0.0001) and greater for the Random Dot E test than for the Randot Preschool test (p = 0.02). For all children, testability on the gross stereo task was greater for the Stereo Smile (77%; p < 0.0001) and Random Dot E (74%; p = 0.005) tests than for the Randot Preschool test (56%) but did not differ significantly between the Stereo Smile and Random Dot E tests (p = 0.19). There were no significant differences among the proportion of children able to complete the gross stereo task among those who were testable on the pretest (p > 0.12, all comparisons).
CONCLUSIONS: Among preschoolers aged 3 years 0 months through 3 years 6 months, testability differs significantly across the three commercially available random dot stereotests evaluated. The results suggest that two-choice procedures increase testability of young preschoolers.