Normative Values, Testability, and Validity for a New Preferential Looking Stereoacuity Test

Abstract

Introduction: Age norms and testability for 3-5 year old children have been reported for the PASS III stereotest using a pointing response. We aimed to expand the normative data to children as young as 6 months, assess testability, and evaluate validity use of the PASS III as a preferential-looking test for younger children and children with special needs. Methods: 68 control children, 362 children with eye conditions, and 167 children with special needs were tested with the PASS III. Percent testable was calculated for children with and without special needs, normal tolerance limits were determined, and test validity was assessed. Results: In controls, mean PASS III stereoacuity improved from 371 arcsec at 12 months to 174 arcsec at 24 months, and 87 arcsec at 36 months. Testability in the 12, 24, and 36 months age groups were 81%, 87%, and 97% respectively and 92% for special needs children. Comparison to previously published norms and testing in a known nil stereoacuity cohort supported PASS III test validity. Compared to gold standard stereoacuity tests, accuracy of the PASS was 89%. Conclusion: Overall, preferential-looking tests using the PASS III provide a sensitive and specific measure of stereoacuity with high testability for young children and children with special needs.

Keywords: PASS III; Stereoacuity; child; infant; special needs.

Figure 1.

Normative stereoacuity by age group. Mean stereoacuity for each age group is indicated by an X. Median stereoacuity for each age group is shown as a thick horizontal line. The lower and upper boundaries of each box represent the 25^th and 75^th percentiles, respectively. The lower and upper whiskers indicate the 5^th and 95^th percentiles respectively.

Figure 2.

Testability of the PASS III test by age group for children with and without eye conditions (combined) and for children with special needs. The percentage of successful tests is indicated to the right of each black bar. Tests were scored “unable” if the child refused to wear the polarized glasses or if the child failed the pretest.

Figure 3.

Comparison of normative test results for 3-, 4- and 5-year olds from the current study, gathered using preferential-looking responses, and two earlier studies of PASS III stereoacuity in normal controls that used pointing responses.