Stability of near stereoacuity in childhood intermittent exotropia

Purpose: To investigate the course of near stereoacuity in a cohort of children with untreated intermittent exotropia. Methods: A total of 95 children ages 2-16 years with untreated intermittent exotropia were identified who had measurements of near stereoacuity using the Preschool Randot (PSR) test on at least 2 successive examinations, with no intervening treatment. Deterioration was defined as a drop of at least 3 octaves, as determined by test-retest data. Alternative secondary analyses were performed defining deterioration as a drop of at least 2 octaves or as a transition from normal to subnormal. The main outcome measure was the deterioration rate calculated at 1 and 2 years using a Kaplan-Meier survival analysis. Results: For near stereoacuity, the rate of decreasing 3 or more octaves was 2% (95% CI, 0%-6%) at 1 year and 7% (95% CI, 0%-16%) at 2 years. The alternative secondary analyses revealed similar low deterioration rates. In most cases of apparent deterioration, near stereoacuity returned to baseline levels without treatment. Conclusions: For children with untreated intermittent exotropia, deterioration in near stereoacuity at 1 and 2 years is infrequent. Therefore, performing surgery for intermittent exotropia to proactively prevent deterioration of near stereoacuity cannot be justified. Retesting stereoacuity is critical to determine whether any measured decrease in stereoacuity is real.