To investigate how the constancy of intermittent exotropia affects postoperative motor and sensory outcomes.

A retrospective analysis was conducted of 44 patients with intermittent exotropia (IXT group) and 16 patients with constant exotropia with a previous history of intermittent exotropia (CXT group). All patients were followed up for more than 1 year postoperatively. Successful postoperative motor alignment was defined as within 8 prism diopters of exo- or esotropia at 6 meters and 33 centimeters. Successful sensory outcome (bifixation) was considered as stereoacuity ≤60 seconds of arc. The influence of constancy, age at surgery, duration of strabismus, preoperative gross stereopsis, preoperative distant deviation, and preoperative distant fusion to surgical outcomes were evaluated using logistic regression analysis.

Mean age at surgery and follow-up periods was 9.34 years and 37.8 months in the IXT group, and 10.19 years and 45.7 months in the CXT group. Successful motor alignment rates of the IXT and CXT groups were 65.9% and 48.3%, respectively. Postoperative bifixation rates of the IXT and CXT groups were 70.5% and 12.5%, respectively. The IXT group showed significantly better successful sensory outcome ( p = 0.000), but no significant difference in motor outcome ( p = 0.121). Constancy and preoperative distant fusion were associated with post-operative bifixation in univariate regression analysis ( p = 0.001, 0.025, respectively). However, only the constancy was strongly associated with successful sensory outcome in multivariate regression analysis with an odds ratio of 20.138 ( p = 0.008).

Surgical correction of intermittent exotropia during the intermittent period showed better sensory outcome than in constant deviation period.