Pharmacologic injection treatment of comitant strabismus

Abstract

Purpose To report the magnitude and stability of corrections in comitant horizontal strabismus achieved by injecting bupivacaine (BPX, optionally with epinephrine) and botulinum A toxin (BTXA) into extraocular muscles of alert adult subjects with electromyographic (EMG) guidance. Subjects & Methods A total of 55 adults with comitant horizontal strabismus participated in a prospective observational clinical series. Of these, 29 previously had undergone 1 or more unsuccessful strabismus surgeries; 4 had undergone other orbital surgeries. Thirty-one patients with esodeviations received BPX injections in a lateral rectus muscle, some with BTXA in the medial rectus; 24 patients with exodeviations received BPX in a medial rectus muscle, some with BTXA in the lateral rectus muscle. A second treatment (BPX, BTXA, or both) was administered to 27 patients who had residual strabismus after the first treatment. Five patients required additional injections. Clinical alignment was measured at 6 months and yearly thereafter through 5 years’ follow-up, with mean follow-up of 28 months. A successful outcome was defined as residual deviation ≤10Δ. Results On average, presenting misalignment of 23.8Δ (13.4°) was reduced at 28 months by 16.0Δ (9.1°), with successful outcomes in 56% of patients. Of patients with initial misalignments ≤25Δ, 66% had successful outcomes, with corrections averaging 13.2Δ (7.5°); of patients with larger misalignments, 40% had successful outcomes, with corrections averaging 20.9Δ (11.8°). Corrected alignments were stable over follow-ups as long as 5 years. Conclusions Injection treatments resulted in stable, clinically significant corrections in comitant horizontal strabismus. Injection provides a low-cost alternative to incisional strabismus surgery, particularly where it is desirable to minimize surgical anesthesia and avoid extraocular scarring.

Expression of schizophrenia biomarkers in extraocular muscles from patients with strabismus: an explanation for the link between exotropia and schizophrenia?

“…Accordingly, if gene expression changes affected primarily or exclusively the opposing (not resected) muscle type rather than the resected muscle type, we would have missed this in our approach. However, based on recent findings implicating the agonist as a major contributor to the deviation in horizontal strabismus ( Debert et al, 2016 ), we consider it unlikely that the muscle type operated upon would not show any relevant gene expression changes.…”

“…1 . The finding that regeneration of the agonist muscle after injection of a myotoxin, without any direct manipulation of the antagonist, can significantly reduce the misalignment ( Debert et al, 2016 ), indicates that the agonist (medial rectus muscle in exotropia, lateral rectus muscle in esotropia) is indeed dysfunctional, although contributions of the antagonist may exist as well. It is also important to emphasize that changes in gene expression in EOMs from strabismic people do not imply that the etiology of the strabismus necessarily derives from the muscle itself, since changes in gene expression may be in response to altered demand or in response to innervational imbalance ( Von Noorden & Campos, 2002 ; Lennerstrand, 2007 ).…”

“…For the purposes of the current study, we are not making any assumptions about primary causes of the strabismus. We do make the assumption that the agonist (that is available for analysis) is substantively involved in deviations, based on recent evidence ( Debert et al, 2016 ).…”

“…The two possibilities are not mutually exclusive. Recent work indicates that the agonist can be rebuilt in horizontal strabismus and that rebuilding at an appropriate muscle length aligns the eyes, indicating that properties of the agonist in strabismus are mechanistically involved ( Debert et al, 2016 ). The cartoon also shows the second possible site of impairment, the innervational control, which is thought to also cause strabismus (for a detailed discussion of the causes of strabismus, see Von Noorden & Campos, 2002 ; Von Bartheld, Croes & Johnson, 2010 ).…”

What's new for us in strabismus?

“…Bupivacaine, an amide local anesthetic, has been proved to correct strabismus by increasing the strength of the muscle. [ 34 ] According to a recently published study[ 35 ] reporting the efficacy of injection treatment in horizontal comitant strabismus in adult patients with bupivacaine and botulinum A toxin, the injection treatments result in a stable clinically significant correction and can be a low-cost alternative to the conventional surgery. Although the success rates are inferior as compared to the conventional surgery, the pharmacologic injection treatment appears promising.…”