Long-Term Outcomes of Intermittent Exotropia: A Real-World Longitudinal Cohort Study of 415 Patients

<i>Background and Objectives</i>: Intermittent exotropia (IXT) is a common childhood strabismus with variable natural history and no universally accepted first-line management. We aimed to characterize long-term real-world outcomes and identify factors associated with alignment stability across surgical and non-surgical strategies. <i>Materials and Methods</i>: This retrospective single-center cohort study reviewed consecutive patients with IXT managed between January 2008 and March 2024. Clinical data included IXT subtype, prism and alternate cover test measurements, binocular control (ECS), stereopsis, refractive error, and treatments (observation, over-minus lenses, and surgery). Postoperative success was defined as ≤10 prism diopters (PD) of eso/exophoria without diplopia. Longitudinal refractive change was analyzed using linear mixed-effects modeling, and time to alignment failure (≤±10 PD at near and distance) was evaluated using Kaplan-Meier and Cox regression analyses. <i>Results</i>: A total of 415 patients were included (mean follow-up 53.2 ± 47.8 months). Over-minus therapy was used in 252 (60.7%) patients for a median of 24 months, and 61 (14.7%) achieved spontaneous alignment. At the final visit, combined near-and-distance alignment success was 41.0% (170/415). Among surgically treated patients (n = 167), motor success was 65.3% (109/167), with reoperation required in 12.6% (21/167). Kaplan-Meier analysis showed cumulative alignment survival of 0.899 at 1 year, 0.563 at 5 years, and 0.302 at 10 years (median 70 ± 4.7 months). In Cox modeling, surgery was strongly protective (HR 0.174), while older age (HR 1.040 per year) and poor baseline distance control (HR 1.421) increased the risk of failure; over-minus therapy was not independently associated with survival. Both treatment groups showed a similar myopic shift over time (β = -0.25 D/year), with no between-group difference. <i>Conclusions</i>: In this longitudinal cohort, intermittent exotropia showed a variable course, with many patients ultimately requiring surgery despite initial non-surgical management. Long-term success was more closely tied to preoperative control quality than age. These findings support an individualized, control-based approach to treatment planning and timing of intervention.