Efficacy of botulinum toxin injection in treating primary inferior oblique overaction: A retrospective cohort study

Objective To evaluate the efficacy and short-term safety of botulinum toxin type A (BTX-A) injection into the inferior oblique muscle for treating inferior oblique overaction (IOOA) in a pediatric cohort. Methods We conducted a retrospective cohort study at King Khaled Eye Specialist Hospital & Research Center, Riyadh, Saudi Arabia, including children aged 2–15 years with IOOA treated with BTX-A injections between June 2022 and September 2024. Data on demographics, baseline IOOA grade, associated strabismus, and postoperative complications were collected. All included eyes had a baseline IOOA grade of 2+ to 4+ and underwent a 5.00 units injection of BTX-A (Botox, Allergan Inc., Irvine, California, USA) to the inferior oblique muscle in a trans-conjunctival technique. The primary outcome was IOOA resolution, defined as postoperative IOOA grade of 0 or +1 at three months following the injection. Results Twenty-three patients (42 eyes) were analyzed. Median age was 6 years (IQR: 5–8), with 56% were female. Bilateral IOOA was present in 83% of included patients, esotropia in 91%, and exotropia in 9%. Three months after injection, 54% of eyes achieved complete or near complete IOOA resolution, and 76% improved by at least one grade. Exotropia decreased from 36% at two weeks to 5% at three months ( p < 0.001), while ptosis declined from 29% to 2% ( p < 0.001). Conclusions BTX-A injection into the IO muscle is effective and safe for primary IOOA, with significant short-term improvement and minimal transient complications. The long-term sustainability of the IOOA improvement post BTX-A injection is unknown.