A study recently published in the American Journal of Ophthalmology compared the efficacy of botulinum toxin injections to strabismus surgery in children with acute acquired comitant esotropia (ACE) and evaluated factors that predicted treatment success.
Give me some background first.
ACE is a presentation of strabismus often characterized by moderate- to large-angle esotropia.
Of note: ACE can not only interfere with the development of binocularity, but is also a risk factor for amblyopia.
And bringing strabismus surgery into this …
While incisional strabismus surgery has been considered the standard of care for managing ACE, previous studies have shown that injecting botulinum toxin into the extraocular muscles is non-inferior to bilateral medial rectus muscle recessions.
Now talk about the study.
In this international, multi-center, non-randomized comparative study, investigators compared the results from cloud-based surveys sent to surgeons who performed a single surgical intervention on children aged 2-17 years with ACE.
Participants received either botulinum toxin injection (“chemodenervation” group) or strabismus surgery (“surgery” group).
In total, 44 surgeons from 19 centers contributed to the study, which included 74 patients in the chemodenervation group and 97 patients in the surgery group.
What were the main outcome measures?
The primary measure was the success rate at 6 months in the propensity-matched cohort—defined as the total horizontal deviation of 10 prism diopters or less with evidence of binocular single vision.
Secondary measures were risk factors for poor outcomes in the full cohort.
Remind me what propensity matching means.
Propensity matching is when researchers use statistical techniques to create an artificial control group by matching each treated participant with a non-treated participant of similar characteristics.
The result: Enabling them to estimate the impact of an intervention.
Findings?
In the propensity-matched data (n=98), the success rate was found to not be significantly different at:
- 6 months (p=0.2)
- Chemodenervation group 70.2%
- Surgery group 79.6%
- 12 months (p=0.2)
- Chemodenervation group 62.9%
- Surgery group 77.8%
However, the success rate was significantly lower in the chemodenervation group at 24 months (52% vs. 86.4%, p=0.015).
Talk about the factors that impacted success rates.
Regardless of treatment modality, treatment delay was associated with a lower success rate at 6 months and was an independent risk factor for poorer sensorimotor outcomes at all postoperative time points in the study.
The median time from onset to intervention in the success group was 4.5 months (interquartile range [IQR] 2.1-6.7) and 7.7 months (IQR 5.6-10.1) in the failure group (P<0.001).
Tell me more.
Additionally, the presence of amblyopia was associated with lower success rates at all time points, regardless of the type of intervention.
Researchers found that the angle of esotropia had no influence on the success rate of chemodenervation or surgery.
Expert opinion?
According to the study authors, “While the benefits of chemodenervation were not as long lasting in the present study as with incisional surgery, and non-inferiority analysis does not support chemodenervation being non-inferior to incisional surgery, there are still reasons to continue to offer chemodenervation as an option.”
Reasons for pursuing chemodenervation in children with ACE include:
- Less invasive nature
- Lower barrier to early intervention
- Lower cost
- Potential for equal or better outcomes with repeat injections
- Easier access to care
Take home.
These findings suggest that in children with ACE, the success rate of chemodenervation was similar to that of the surgery group for up to 12 months, but diminished at 24 months.
Additionally, participants with prompt intervention and no amblyopia had the most favorable outcomes, irrespective of treatment modality.