An eccentric presentation of transient bilateral mydriasis after botulinum toxin injection: A case report

Botulinum toxin (Botox) can be used to manage strabismus due to its efficacy in inducing muscle paralysis by blocking acetylcholine release. Botox is an important treatment for many conditions in ophthalmology; however, clinicians must be aware of its potential complications, such as mydriasis. Mydriasis is defined as dilation in the pupils, and it can be divided into two subsets: transient and persistent mydriasis.

This report presents a case of a 4-year-old child having esotropia (ET) with an angle of 30 Prism Dioptre (PD) and Inferior Oblique muscle Overaction (IOOA). The patient was scheduled for Botox injection to correct ET and IOOA and developed transient bilateral mydriasis.

Botox is a valuable therapeutic intervention in pediatric ophthalmology. A potential side effect of it is transient mydriasis, which developed in this patient. Interestingly, a higher dose of Botox injected a second time didn't result in mydriasis, which depicts a potential variability in patient responses to Botox. The mechanisms behind this adverse effect and its occurrence regardless of the dose remain unclear, but proposed hypotheses suggest that toxin diffusion could impact nearby structures, such as the ciliary ganglion or pupillary sphincter muscle, leading to pupil dilation. In addition, this case highlights the importance of vigilant post-injection monitoring. Further research and investigation are warranted to elucidate the possible underlying mechanisms in order to provide guidance for clinical practice.

Collectively, our results confirm that the patient developed transient bilateral mydriasis as a result of Botox injection.