Purpose-Distance stereoacuity is used to monitor deterioration of intermittent exotropia (intermittent XT), but variability of stereoacuity has not been rigorously studied. The purpose of this study was to assess the variability of stereoacuity over one day, in children with intermittent XT.Design-Prospective cohort study.
Methods-Setting: Clinical practice.Patient population: Twelve children with intermittent XT.Observation procedures: Stereoacuity was assessed using the Frisby Davis Distance and Distance Randot at distance and the Frisby and Preschool Randot at near. Tests were repeated 3 or 4 times over the day, with at least 2 hours between assessments.Main outcome measure: 'Variable' stereoacuity defined as a change by 2 or more log levels between any 2 time points over the day.Results-Variable stereoacuity at distance was found in 5 (42%) of 12 patients. Four (33%) of 12 patients were variable using Distance Randot test, 3 of whom also varied using Frisby Davis Distance. One patient was variable using Frisby Davis Distance only. Nine (75%) of 12 patients completed near stereoacuity testing; 2 (22%) of 9 showed variable near stereoacuity. Two (22%) of 9 were variable using Preschool Randot, 1 (11%) of whom also varied using Frisby. In some cases stereoacuity changed from measurable stereoacuity on one assessment to nil on another.Conclusions-Nearly half of children with intermittent XT show marked changes in stereoacuity over the course of a single day. When based on isolated measures, an apparent change in distance stereoacuity between visits should be interpreted with caution.