Hypoplastic lateral rectus muscle in a 39-year-old female with esotropia

Congenital hypoplasia of the extraocular muscles is a rare cause of strabismus. This article aims to report the case of a 39-year-old female with esotropia and a hypoplastic lateral rectus muscle (LRM).

Case report.

The patient presented with esotropia measuring 35 prism diopters (PD), no evidence of stereoptic vision, and an otherwise normal examination. No surgery had ever been performed on her LRMs. During surgery for bilateral LRM resection, her left LRM was revealed to be severely hypoplastic, allowing for muscle hooks to be visible under the muscle sheath. Her surgery was successful.

The patient's presentation and history may suggest myogenic etiology, rather than neurogenic. Diagnosis of Duane's syndrome did not match our differential; we thus hypothesize a congenital, structural hypoplasia of the left LRM. Cases such as the one described are important for timely diagnosis and tailored surgery planning.