Botulinum toxin injection in the patients with Duane syndrome type 1

Purpose: To evaluate the efficacy of botulinum toxin injection in the patients with type 1 Duane syndrome and identify the predictive factors for success. Methods: Sixteen patients with esotropic type 1 Duane syndrome without history of ocular surgery were selected for this interventional case series. The botulinum toxin was injected in the medial rectus of all patients. Visual acuity, dry refraction, cyclo-refraction, ocular motility, and amount of deviation were measured. Complete success, partial success, and failure were defined as residual deviation/face turn less than 8 prism diopters (PD)/5, 8-20 PD/5-15, and equal or greater than 20 PD/15, respectively. Results: Sixteen cases (6 males) were included in our study. The mean esotropia was 26.27 ± 8.35 (12-40 PD) which was reduced significantly to 13.5 ± 12.39 PD during 6 months follow-up (p < 0.001). Face turn was improved significantly from a preoperative mean of 18.27 to: 0.094 at 1 week, 0.11 at 1 month, 3.31 at 3 months, and 7 at 6 months (p < 0.001). Complete success was seen in 6 patients (37.5%), partial success in 4 patients (25%), and failure in 6 patients (37.5%). There was a significant relation between the amount of forced duction testing (FDT) and the success rate (p: 0.019). No complication was seen during injections. Conclusions: Botulinum toxin could be an alternative treatment in Duane syndrome with appropriate case selection. FDT could be a predictive factor for response to botulinum toxin.