الفهرس 
Acknowledgements
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Abstract
This was a prospective randomized interventional study to determine the effectiveness of intraoperative botulinum toxin A augmentation compared to surgery alone in large angle horizontal deviations The study included 19 patients with large angle horizontal strabismus (≥55 PD). Patients were randomly allocated to 2 groups (10 in surgery only group ‘group I’ and 9 in BTA augmented surgery group ‘group II’). We compared between the 2 groups regarding success rate and treatment effect. Treatment was considered successful if the patients had orthotropia ±10 PD at their final examinations. The treatment effect (alignment change in in prism diopters per amount of surgery in mm ‘PD/mm’) was calculated and compared between the study groups at all follow up intervals. The success rate was greater for BTA augmented surgery group compared to conventional surgery group (77.78% versus 70% respectively), but this difference was not statistically significant (P value 0.701). The treatment effect was greater in BTA augmented surgery group comparted to conventional surgery group at all follow up durations, but this difference was not significant at ≥ 6 months follow up (5.38 ± 1.54 vs 4.65 ± 1.16 PD/mm, P value 0.211). However, subgroup analysis revealed a significant difference in treatment effect at ≥ 6 months follow up between esotropic patients treated with BTA augmented bilateral MR recession compared to esotropic patients treated with surgery alone (6.7 ± 0.4 vs 4.9 ± 1.2 PD/mm, P value = 0.038). In conclusion, botulinum toxin augmented surgery is not inferior to surgery alone in treatment of different types of large angle concomitant horizontal deviations. BTA augmentation is particularly more effective in patients with large angle esotropia treated with bilateral MR recession. BTA use reduces the surgical dose and the need for 3 to 4 rectus muscle surgery, thus minimizing the risk of late consecutive deviations. Botulinum toxin related adverse effects are transient and resolve spontaneously within less than 3 months.