Cosmetic Bont-A–Induced Transient Esotropia

PURPOSETo present a rare case of transient esodeviation and binocular diplopia caused by unintended medial rectus involvement following periocular botulinum toxin type A (BoNT-A) injection performed in a non-medical setting.

CASE REPORTA 39-year-old female with no systemic disease presented with a 1-day history of painless horizontal binocular diplopia. Five days before symptom onset, she had received a cosmetic BoNT-A injection into the glabellar, forehead, and lateral canthal regions at a non-medical beauty center. Ophthalmic examination revealed a visual acuity of 0.0 logMAR bilaterally, normal anterior and posterior segment findings, and a 10-prism-diopter esodeviation in primary gaze. Extraocular motility demonstrated full ductions without restrictive patterns. Worth four-dot testing showed right-eye suppression, and stereopsis was markedly reduced. Cranial nerve and neurological examinations were normal. Orbital–cranial CT and MRI were unremarkable. The clinical picture was consistent with unintended diffusion of the toxin, leading to transient medial rectus overaction. The patient was managed conservatively with prism correction. Prism strength was gradually reduced over follow-up (8 PD → 6 PD → 2 PD), and prisms were discontinued by month four. Full resolution of diplopia occurred at month six, consistent with the expected timeframe of neuromuscular recovery after BoNT-A exposure.

CONCLUSIONMedial rectus involvement following cosmetic BoNT-A injection is extremely rare but may result in symptomatic diplopia and functional visual impairment. This case emphasizes that botulinum toxin injections must be performed exclusively by trained medical professionals with appropriate anatomical knowledge. Early recognition of cosmetic injection–related strabismus is essential to avoid unnecessary neurological workup and to ensure timely conservative management.

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