Surgical Outcomes of Intermittent Exotropia in Adults: A Systematic Review

Adult intermittent exotropia (IXT) is less well studied than paediatric IXT, yet counselling is challenging due to postoperative exodrift, diplopia risk, and differing functional expectations. This systematic review synthesised surgical outcomes for adult (≥18 years) IXT. A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020-guided systematic review of PubMed/MEDLINE was performed using two searches ("surgical" AND "outcomes" AND "exotropia"; "surgery" AND "intermittent exotropia"), limited to English-language human studies published within the last 10 years. Eligible studies reported postoperative motor alignment and/or reoperation, diplopia, drift, or binocular outcomes in adults with IXT. Motor success was narratively standardised to ≤10 prism dioptres (PD) of orthotropia at distance (allowing ≤5 PD esodeviation where applicable). Risk of bias was assessed using the Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I). Due to heterogeneity in outcomes and follow-up, meta-analysis was not undertaken. Six studies (one randomised prospective interventional study and five retrospective cohorts) comprising 552 participants were included. Mean age ranged from 27 to 42 years, and preoperative distance deviation was typically 30-40 PD (one study >50 PD). Reported motor success ranged from 47.6% to 90% across primary endpoints of three months to two years or longer, with most studies demonstrating progressive exotropic drift over time. Diplopia was generally transient and varied by early postoperative alignment and intervention. No major adverse events occurred, and a low reoperation rate was reported. Overall risk of bias was serious in most studies, primarily due to confounding and selection bias. Adult IXT surgery achieves moderate-to-high motor success, but outcomes vary with technique, early alignment, and follow-up duration. Prospective adult-only studies with standardised endpoints and patient-centred outcomes are needed.