Stereoacuity thresholds before and after visual acuity testing

Purpose: To compare stereoacuity thresholds before and after visual acuity testing in patients with intermittent strabismus and in controls. Design: Prospective cohort study. Participants and Controls: Eighty-eight patients (41 with intermittent strabismus and 47 controls) with measurable stereoacuity on their initial stereoacuity test were enrolled prospectively. Methods: Stereoacuity was measured before and immediately after visual acuity testing using the near Preschool Randot and Distance Randot stereotests. Stereoacuity was transformed to log units for analysis. Main Outcome Measures: Change in stereoacuity thresholds (log seconds of arc [arcsec]). Results: There was no overall deterioration in distance stereoacuity or near stereoacuity thresholds in either the intermittent strabismus or control groups. The mean change for patients with intermittent strabismus was 0.02 log arcsec (95% confidence interval [CI], -0.02 to 0.06) for near stereoacuity and 0.04 log arcsec (95% CI, -0.01 to 0.09) for distance stereoacuity. Control patients demonstrated a mean change of 0.03 log arcsec (95% CI, -0.01 to 0.06) for near stereoacuity and 0.01 log arcsec (95% CI, -0.06 to 0.08) for distance stereoacuity. These mean changes correspond to less than approximately one eighth of an octave. For individual patients, deterioration in stereoacuity beyond previously reported test-retest variability (0.6 log arcsec or more) was not observed in patients with intermittent strabismus or controls using either test. Conclusions: Stereoacuity thresholds do not deteriorate after visual acuity testing, and therefore measurements of stereoacuity do not need to precede visual acuity measurement or other tests that involve short periods of dissociation. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.