Long-Term Follow-up of Botulinum Toxin Injection in Treatment of Infantile Esotropia: Outcomes and Predictive Factors for Success

Abstract

INTRODUCTION: RInfantile esotropia (IE) is the most common type of childhood esodeviation. Its treatment goal is to achieve enough microtropia and isoacuity to provide binocular cooperation. Since botulinum toxin (BT) is rising as a less invasive treatment, we aim to evaluate its long-term results and determine if there are any predictive factors for success.
METHODS: We retrospectively reviewed infantile esotropia patients’ records who had BT injections as a first-line treatment between 2017 and 2023 at our centre. We examined angles before and after the procedure, BCVA, binocular functions and the need for additional treatment. Complete success was defined as an angle ≤10 PD; partial as at least a 50% reduction but >10 PD, with other cases considered failures.
RESULTS: We included 101 patients with a mean age of 4.77±3.54 years. Mean preoperative deviation angle was 30±11.82 PD. A total of 58.4% of patients had isoacuity regarding BCVA. The change in the mean angle at 3, 6, 12 months and last obtained after procedure was 24.74±11.89 PD (p-value<0.001); 19;18±12.01 PD (p-value<0.001); 16.04±14;79 PD (p-value<0.001) and 15.67±12.70 PD (p-value<0.001) respectively. Microtropia at 3, 6, 12 months and last obtained was achieved in 73.3%, 45.5%, 24.8% and 25.6% respectively. Isoacuity was achieved in 64.4% of patients and binocular cooperation in 28% of cases. Twenty-four patients (23.8%) underwent a second injection and 19 patients (18.9%) needed secondary surgery. Early microtropia significantly increased the time needed to a new BT injection (p-value=0.005) as well as the need for secondary strabismus surgery (p-value=0.002). Simultaneously, receiving the first injection at an earlier age seemed to significantly influence last obtained BCVA (p-value=0.042) and binocular cooperation (p-value=0.023,) but not the degree of microtropia (p-value=0.588).
CONCLUSION: To the best of our knowledge, this is the largest European study concerning long-term follow-up of infantile esotropia after BT injection. We noted complete success in most cases, as well as improvements in binocular cooperation and isoacuity over time. These results continue to support the role of BT injection as a first-line treatment, as early as possible, potentially delaying surgery.