Three-year observation of children 12 to 35 months old with untreated intermittent exotropia

Abstract

Purpose: To describe the clinical course of untreated intermittent exotropia (IXT) in children 12-35 months of age followed for 3 years.

Methods: We enrolled 97 children 12-35 months of age with previously untreated IXT who had been randomly assigned to the observation arm of a randomised trial of short-term occlusion versus observation. Participants were observed unless deterioration criteria were met at a follow-up visit occurring at 3 months, 6 months, and 6-month intervals thereafter for 3 years. The primary outcome was deterioration of the IXT by 3 years, defined as (1) a constant exotropia ≥10 prism dioptres (∆) at distance and near (i.e., motor deterioration) or (2) treatment prescribed despite not having met motor deterioration. The primary analysis used the Kaplan-Meier method to determine the cumulative proportion of participants meeting deterioration by three years and 95% confidence interval (CI).

Results: The cumulative probability of deterioration by 3 years was 28% (95% CI = 20%-39%). Of the 24 participants meeting the primary outcome of deterioration, seven met motor deterioration and 17 were prescribed treatment without meeting motor deterioration. The cumulative probability of motor deterioration by 3 years was 10% (95% CI = 5%-19%).

Conclusions: Given the modest rate of motor deterioration over three years, watchful waiting may be a reasonable management approach in 12- to 35-month-old children with IXT. To confirm this recommendation would require a long-term randomised trial of immediate treatment versus observation followed by deferred treatment if needed.

Keywords: exotropia; intermittent exotropia; observational study; paediatric; strabismus.

Conflict of interest statement

Disclosure: The authors report no conflicts of interest and have no proprietary interest in any of the materials mentioned in this article.

© 2020 The Authors Ophthalmic & Physiological Optics © 2020 The College of Optometrists.

Figures

Figure 1.

Cumulative Proportion of Participants with Deterioration Anytime During three Years (Primary Outcome) Motor deterioration = constant XT of ≥10∆ by Simultaneous Prism and Cover Test (SPCT) at distance and near, confirmed by a retest (95% confidence interval (CI)). Cumulative (%) of participants with motor deterioration by 3 years (95% CI) = 10% (95% CI = 5% to 19%). Deterioration (primary outcome) = motor deterioration or prescribed surgical or nonsurgical treatment without meeting motor deterioration. Cumulative (%) of participants with deterioration by 3 years = 28% (95% CI = 20% to 39%).

Figure 2.

Exotropia Control: Baseline vs. 3-Year Visit for Participants Who Completed the 3-Year Visit and Had Not Been Prescribed Treatment Anytime During the Study (N=53) Figure 2a shows distance control; Figure 2b shows near control. Centre diagonal line represents the same control score for baseline and 3 years. The upper diagonal line indicates worsening of 3 points on a scale between 0 (phoria) and 5 (constant exotropia) based on the 3-point threshold for real change; the lower diagonal line indicates improvement of 3 points.

Figure 3.

Magnitude of Exodeviation by Prism and Alternate Cover Test (PACT) (∆): Baseline vs. 3-Year Visit for Participants Who Completed the 3-Year Visit and Had Not Been Prescribed Treatment Anytime During the Study (N=53) Figure 3a is distance exodeviation magnitude by PACT (∆); Figure 3b is near exodeviation magnitude by PACT (∆). Centre diagonal line represents the same PACT measurement for baseline and 3 years. The upper diagonal line indicates worsening that exceeds published repeatability coefficients based on test-retest data (8∆ for distance PACT and 13∆ for near PACT); the lower diagonal line indicates improvement by those amounts.