Adult small-angle acute acquired comitant esotropia: clinical features and treatment outcomes

<i>Introduction</i>: Acute acquired comitant esotropia (AACE) is a disorder characterized by the sudden onset of horizontal diplopia with comitant deviation across gaze positions. Traditionally considered rare, its incidence has increased in association with prolonged near work and digital device use. While most reports involve children and young adults with larger deviations, small-angle forms in adults remain underrecognized and therapeutically challenging. This study aimed to describe the clinical characteristics, associated risk factors, and treatment outcomes of adult patients diagnosed with AACE with small-angle deviations. <i>Methods</i>: This retrospective observational study included patients diagnosed with AACE at a tertiary center between 2022 and 2024. Included patients had a confirmed diagnosis of AACE, defined by acute-onset diplopia, comitant esotropia with ≤20 prism diopters (PD) in primary gaze, ≤5 PD variation in lateral gaze, and a minimum follow-up of 6 months. Data collected included visual acuity, refractive status, neuroimaging findings, and treatment outcomes. Exclusion criteria included age over 55 years, high myopia (>-6.00 diopters-D-), ocular pathologies inconsistent with AACE, or prior history of amblyopia or strabismus. <i>Results</i>: The cohort included 16 patients (mean age 36.9 ± 7.7 years; 62.5% male). All presented with distance diplopia; four (25%) also had diplopia at near. Mild myopia (≤-1.00 D) was present in 75% of cases, with overall myopia in 87.5%. Mean esodeviation measured 7.94 ± 5.76 prism diopters (PD) at distance and 0.50 ± 1.51 PD at near. Most patients (81.3%) reported more than 6 hours per day of digital device use. Neuroimaging was normal in all cases. Initial treatments included surgery (<i>n</i> = 9), botulinum toxin injection (<i>n</i> = 7), prisms (<i>n</i> = 3), and observation (<i>n</i> = 2). Four patients required sequential therapies. Surgical outcomes were successful in 88.9% of cases, with botulinum toxin achieving resolution in 71.4%. Ultimately, 87.5% of patients experienced complete resolution of diplopia, without treatment-related complications. <i>Discussion</i>: AACE appears to be associated with excessive use of electronic devices, predominantly affecting young males with previously normal binocular vision. Early diagnosis and individualized treatment - particularly minimally invasive surgery or botulinum toxin - are effective and safe approaches.