Botulinum Toxin Injection in Horizontal Rectus Muscles Without Electromyography Using an Open Sky Versus a Closed Sky Technique

To ascertain whether electromyographic control when injecting botulinum toxin in the horizontal rectus muscles is necessary, and to compare the open sky and closed sky injection techniques that are used without electromyographic control.The records of 135 patients with horizontal strabismus who received botulinum toxin injections were reviewed retrospectively. Sevoflurane or propofol anesthesia was used in children, and topical benoxinate hydrochloride was used in adults. Patients received a bilateral injection of 2.5 to 15 IU of botulinum toxin, without electromyographic control, into the medial or lateral rectus muscles to correct esotropia or exotropia, respectively. An open sky technique was used in 31 patients, and a closed sky technique was used in 104 patients. Postoperative alignment within 10 prism diopters (PD) of orthotropia was considered a successful outcome.A successful outcome at 6 months of follow-up was achieved in 47% of all patients: 59% of patients in the open sky group and 44% of patients in the closed sky group (P = .151). Botulinum toxin injection corrected a mean of 14 ± 9.705 PD in patients in the open sky group and 31 ± 20.589 PD in patients in the closed sky group to obtain mean residual angles of 21 ± 16.692 and 13 ± 11.901 PD, respectively.The results obtained without electromyographic assistance were not remarkably different from the studies using electromyographic control. Moreover, because the results of the open sky technique were not significantly superior to the closed sky technique, the latter was favored to shorten the operative time and postoperative convalescence, and to reduce the risk of postoperative adhesions and scarring, which made re-operations difficult. [J Pediatr Ophthalmol Strabismus. 2022;59(6):388-395.].