Holmes, Jonathan M.

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.