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.

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 ≤10(Δ).

Results: On average, presenting misalignment of 23.8(Δ) (13.4°) was reduced at 28 months by 16.0(Δ) (9.1°), with successful outcomes in 56% of patients. Of patients with initial misalignments ≤25(Δ), 66% had successful outcomes, with corrections averaging 13.2(Δ) (7.5°); of patients with larger misalignments, 40% had successful outcomes, with corrections averaging 20.9(Δ) (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.

FIG 1

Binocular alignment time course. Primary position gaze alignment (PP gaze) is shown with patients grouped into cohorts according to how long we were able to follow them. The number of patients in each cohort is given by the label near its color-coded curve. Follow-up times are measured from the time of the final treatment. (All 55 patients had initial alignment measures, and all but one had measurements at 6 months.)

FIG 2

Alignment is more sensitive to muscle length than to force. Effects on primary position of increases in force of a BPX-injected muscle, compared to length-adaptive changes in lateral rectus and medial rectus muscles, as predicted by Orbit 1.8.