Progression of intermittent exotropia in surgical and non-surgical patients: a retrospective cohort study

Intermittent exotropia (IXT) is a common form of childhood strabismus, and greater exodeviation or poorer control at presentation are known factors influencing the decision to pursue surgery. However, existing studies have not tracked pre-operative progression longitudinally or directly compared these changes between patients who undergo surgery and nonsurgical controls. This study aimed to compare the clinical features and pre-operative progression of IXT between surgically and nonsurgically managed children matched by duration of follow-up.

The medical records of patients < 19 years diagnosed with IXT from 1 January 2002, through 31 August 2023 at a single institution were retrospectively reviewed. Patients with premature birth, neurologic disease, developmental delay, or other forms of exotropia were excluded. All patients who underwent surgery were observed from diagnosis until strabismus surgery was recommended and matched one-to-one with non-surgically-managed controls based on a similar observation duration. Control was assessed at distance and near using a standardized office-based severity scale ranging from 0 to 5.

Eighty-one surgical patients diagnosed with IXT were matched with 81 non-surgical patients with IXT. Surgical patients (49 female, median age 3.7 years) were followed for a median of 23 months compared to 27 months for non-surgical patients (48 female, median age 4.0 years). Surgical patients had worse initial median distance control (2.3 vs 2.0; p = .004) and near horizontal exodeviation (25.0 prism diopters [PD] vs 20.0 PD; p = .035) compared to controls. After the pre-operative observation period, surgical patients demonstrated worse control and horizontal exodeviation at both distance (4.0 vs 2.0; 30.0 PD vs 25.0 PD; p < .001) and near (2.0 vs 1.0; 28.9 PD vs 21.6 PD; p < .001).

Children who ultimately underwent surgery for intermittent exotropia not only presented with more severe disease but also demonstrated objectively greater deterioration in control and exodeviation during observation than matched nonsurgical peers. These findings underscore the progressive nature of clinically significant IXT and highlight the utility of serial, office-based control assessments in identifying patients likely to require surgery.