Efficacy of Botox Injections for Acquired Esotropia Declines with Age

In a study evaluating the two-year efficacy of Botox injections for patients of varying ages with AACE, the results suggested that the presence of preserved or restored stereoacuity is a significant predictor for lower recurrence rates. Photo: Sgfin/Wikimedia Commons. Click image to enlarge. While currently only estimated to make up 0.3% of pediatric strabismus cases, the prevalence of acute acquired comitant esotropia (AACE)—characterized by the acute onset of comitant esotropia with minimal accommodative components and possibly preserved binocular vision—is rising according to recent epidemiological studies. Given that botulinum toxin type A (Botox) injection is one of the mainstay interventions (alongside surgical intervention), researchers sought to evaluate the two-year efficacy of this treatment across various age groups. Their findings revealed a decline in treatment efficacy as age increased. It also concluded that the preservation or restoration of normal stereopsis is a significant predictor for reducing the recurrence risk of AACE.The study, designed as a retrospective clinical cohort analysis, included a total of 276 patients diagnosed with AACE at a single hospital in Zhejiang, China, between 2019 and 2023. Participants were stratified into five distinct age groups: under six years, six to 12 years, 12 to 20 years, 20 to 30 years and over 30 years. The median age of the participants was 18 years, and female patients represented 45.3% of the cohort. Comprehensive pre-treatment evaluations were conducted prior to patients receiving Botox injections, including assessments of ocular motility, BCVA, stereoacuity and measurement of deviation angles. Follow-up appointments took place at one, three, six, 12 and 24 months post-injection to monitor patient outcomes.The overall two-year motor success rate was found to be 69.0%. When analyzing the outcomes by age group, a clear trend emerged demonstrating age-dependent efficacy: the motor success rates were as follows: 86.5% for those aged six years or younger, 80.0% for those between six to 12 years, 74.1% for those aged 12 to 20 years, 67.5% for the 20 to 30 age group and only 44.3% for participants over 30 years old.The study also evaluated the restoration of stereoacuity among patients. Cumulative rates of stereoacuity restoration were documented at various intervals, with 47.6% of patients achieving this by one month post-treatment, increasing to 71.8% by the two-year mark. Patients older than 30 demonstrated significantly lower rates of stereopsis recovery post-treatment compared to younger cohorts, which the researchers believe supports the hypothesis that “patients with compromised binocular vision tend to demonstrate instability in ocular alignment” following Botox treatment.The study also shed light on the factors influencing recurrence rates. It was found that prolonged near work activities and increasing patient age significantly elevated the risk of recurrence for AACE. Specifically, every additional hour spent on near work per day was associated with a 1.1 times increase in the recurrence risk. Furthermore, the presence of preserved or restored stereoacuity emerged as a significant predictor for lower recurrence rates, suggesting that achieving this visual function is crucial for patient prognosis.While some experts believe AACE should be confined to children younger than five, differentiating it from acquired non-accommodative esotropia, the authors of the present study argue that normal binocular vision potential should define AACE rather than strict age limits. They found that "the critical period for binocular visual development" begins at three months and continues until around three years. Among 41 AACE patients aged three to five, 90.2% achieved orthophoria after BTXA treatment, and 72.7% demonstrated normal stereoacuity post-treatment. Based on this positive data, the authors note that their findings “support that AACE can indeed occur in children under five years of age, with this younger cohort demonstrating favorable and stable treatment outcomes” from intervention with Botox injections.In summary, these findings reveal “an inverse correlation between patient age and therapeutic efficacy” of botulinum toxin in AACE management, the authors concluded. “The preservation of binocular fusion potential emerges as a promising prognostic indicator for treatment outcomes and recurrence risk.”Click here for the journal source. Zhang J, Chen X, Zhang R, et al. Efficacy of Botulinum Toxin Type A for acute acquired comitant esotropia: a retrospective cohort study. Am J Ophthalmol. June 2, 2025. [Epub ahead of print].