Botulinum toxin treatment for bielschowsky acquired commitant esotropia in adults.

[BACKGROUND] Many researchers have noticed that there is an increasing trend of Bielschowsky acquired comitant esotropia (ACE) in recent years related to excessive near work, but the exact pathogenesis and treatment methods have not been reported yet. Therefore, we aimed to characterize the clinical features of this ACE in adults and to evaluate the efficacy of botulinum toxin (BTX) injections in these patients.

[METHODS] This was a prospective consecutive case series of 47 patients with Bielschowsky ACE. BTX was injected bilaterally into the medial rectus muscle of 45 patients, and twenty-seven of them (27/45) completed 10 months of follow-up after their last injection. Angle of deviation, fusion, stereopsis, subjective assessment of diplopia were documented before and after BTX treatment, and repeated measures data were compared by the Wilcoxon signed-rank test or Analysis of variance. The relationship between BTX dosage and corrected esotropia was explored by the Regression analysis. Meanwhile, possible risk factors for ACE including time spent on near work, refraction error, patients' personality, glasses wearing habits and duration of symptoms were recorded and analyzed with General Linear Models.

[RESULTS] The patients aged 32.32 ± 10.96 (range 15-53) years spent 8.34 ± 2.38 h on near work each day, and most myope habitually removed their glasses at near. Their chief complaint was distance diplopia, with more significant esotropia at distance (around 20 PD) than at near. This series of patients also exhibited perfectionist tendencies. However, most patients achieved orthophoria after BTX treatment, only with a mild residual esotropia (+ 3.96 ± 5.79 PD), which left them asymptomatic most of the time.

[CONCLUSION] This group of ACE patients was characterized by diplopia with more significant esotropia at distance. Besides excessive near-work, habitually removing myopic glasses and perfectionist tendencies may also contribute to this type of ACE. Fortunately, bilateral BTX injection safely and effectively reduced the esotropia with complete resolution of symptoms, especially for those treated at an early stage.