Risk Factors for Stereoacuity Impairment in Intermittent Exotropia: Results from a Nationwide Korean Study

Abstract

Purpose: To identify clinical factors associated with stereoacuity impairment in patients with intermittent exotropia (IXT), with an emphasis on perinatal, refractive, motor, and sensory parameters. Methods: This nationwide cross-sectional study analyzed 5,385 Korean patients with IXT from the Korean Intermittent Exotropia Multicenter Study (KIEMS). Stereoacuity was assessed using Titmus and Randot stereotests, and patients were classified into good or poor stereoacuity groups. Multivariable logistic regression was performed to identify independent predictors, including anisometropia (≥1.5 D) and refined Worth 4 Dot (W4D) categories (fusion, suppression, diplopia). Results: Among 3,723 patients with Titmus and 952 with Randot results, anisometropia ≥1.5 D was strongly associated with poor Titmus stereoacuity (OR=4.707, p=0.0002). Good distance and near fusion control were protective factors in the Titmus model. An initial surgical plan was also linked to better Titmus stereoacuity. No variables remained significant in the Randot model. Neither prematurity nor low birth weight was independently associated with stereoacuity after adjustment. Conclusions: Anisometropia and fusion control are key predictors of stereoacuity in IXT, whereas prematurity and low birth weight have limited independent effects. Early detection and correction of anisometropia and preservation of fusion control should be prioritized to maintain binocular visual function.