Botulinum toxin injection of the inferior oblique muscles for V-pattern strabismus and primary position hypertropia

Date Published:

2021 Jul 17


PURPOSE: To evaluate outcomes of botulinum toxin (BTX) injection of the inferior oblique (IO) muscles. DESIGN: Retrospective case series. METHODS SETTING: Single center, ophthalmology department at Boston Children's Hospital STUDY POPULATION: All patients treated with IO muscle injection of BTX (onabotulinumtoxinA) between 2010 and 2020. OBSERVATION PROCEDURE: Sensorimotor evaluations at short-term (<2 months), medium-term (2-4 months), and long-term (≥4 months) intervals. OUTCOME MEASURE: Primary outcomes included median improvement in V-pattern strabismus and primary position hypertropia. Secondary outcomes included IO overaction. Wilcoxon signed-rank tests were performed to identify differences pre- and post-injection. RESULTS: Record review identified 20 patients with median age 4.5 [range 1-69] years. Median BTX dose injected (31 IO muscles) was 5.0 [range 3.0-7.0] units. Indications included V-pattern strabismus (N=8), hypertropia (N=7), or both (N=5). Median long-term interval was 6.4 months [range 4.1-26.6]. Injections were concurrent with treatment of horizontal strabismus in all but 3 cases. Median V-pattern magnitude changed from 10 PD pre-operatively to 0 PD short-term (p=0.006) and 3.5 PD long-term (p = 0.34). Median hypertropia changed from 8.5 PD pre-operatively to 1.5 PD short-term (p=0.01) and 8 PD long-term (p=0.87). Median IO overaction grade improved significantly at short-term (p<0.001) and long-term (p=0.007) intervals. There were no complications associated with the IO injections. CONCLUSIONS: BTX injection of the IO muscles can be a useful adjunct to the management of V-pattern strabismus. Intervention for primary position hypertropia may be helpful for short-term relief with no expectation of long-term benefit.

Last updated on 08/02/2021