Distance stereotesting using vision test charts for intermittent exotropia

Purpose: To assess the role of distance stereoacuity using the System Chart SC-1600 Pola (SC) to evaluate intermittent exotropia (IXT). Methods: Stereoacuity testing was performed in 28 children with IXT and 25 age-matched control subjects using the SC test, the distance Randot stereotest for distance, and the Titmus stereotest for near stereoacuity. Ocular alignment control was defined using the revised Newcastle Control Score (NCS). The correlations between the stereotests and NCS were evaluated using Spearman's correlation test. Results: Distance stereoacuity was better in both groups when using the SC test than when using the distance Randot stereotest (median: patients with IXT, 90 arcsec and 400 arcsec; control, 60 arcsec and 100 arcsec; P<0.001 for both comparisons). The two test scores were not correlated in either group (IXT: r(s)=-0.003, P=0.99; control: r(s)=0.37, P=0.07). A positive correlation was found between the distance NCS and SC test scores (r(s)=0.49, P=0.004) and the total NCS and SC test scores (r(s)=0.49, P=0.004). However, no correlation was observed between any NCS and the distance Randot stereotest or Titmus stereotest scores. Conclusion: Stereoacuity, as measured by the SC test, may be an objective measure of IXT control.