# Two Cases of Adult-Onset Esotropia With a History of Medial Rectus Muscle Recession Treated With Botulinum Toxin Type A

## TL;DR

This paper reports two cases where botulinum toxin was used to treat recurring eye misalignment in adults who had previously undergone eye muscle surgery.

## Contribution

The study demonstrates the feasibility of using botulinum toxin in patients with a history of strabismus surgery for recurrent esotropia.

## Key findings

- Botulinum toxin type A injections improved ocular alignment and resolved diplopia in both cases.
- One patient required a second injection due to recurrence of symptoms.
- The treatment was performed using standard techniques despite prior surgery.

## Abstract

Reports on the use of botulinum toxin type A (BTX-A) in patients with esotropia who have previously undergone strabismus surgery are limited. We present two cases of acquired adult-onset esotropia treated with medial rectus recession followed by BTX-A injection and describe the outcomes.

In Case 1, a 49-year-old woman underwent bilateral medial rectus recession for acquired concomitant esotropia. Postoperatively, diplopia resolved, but intermittent recurrence was noted 12 months later. At 26 months postoperatively, BTX-A (2.5 units) was injected into the left medial rectus muscle transconjunctivally under electromyography (EMG) guidance. Diplopia resolved shortly after the injection but recurred three months later, prompting a second injection. Follow-up is ongoing.

In Case 2, a 62-year-old woman with high myopia and mild abduction limitation underwent bilateral medial rectus recession for esotropia, but ocular alignment did not improve. Five months postoperatively, BTX-A (2.5 units) was injected into both medial rectus muscles transconjunctivally under EMG guidance. Although temporary exotropia developed, ocular alignment gradually improved, and diplopia resolved. As of three months after the injection, there has been no recurrence of esotropia, and the patient remains under observation.

In both cases, strabismus surgery and BTX-A injections were performed by the same surgeon. Although the observation period after BTX-A injection was limited to three months in both cases, the treatment was associated with improvement in ocular alignment and resolution of diplopia, while recurrence was noted in one case.

BTX-A injection can be performed using standard techniques, even in patients with a history of strabismus surgery, and may provide temporary improvement in ocular alignment. This report provides illustrative evidence of the feasibility of BTX-A treatment, suggesting that it may be considered as one of the potential options for managing recurrent or undercorrected esotropia following medial rectus recession.