Session: Poster session A

Cyclic esotropia - onset and course before and after treatment with botulinum toxin A injection - Case Report

Introduction: Our aim is to describe a case in which intermittent esotropia (ET) became cyclic esotropia and how it responded to botulinum A toxin (BTX) treatment.

Methods: We describe the clinical findings (VA, stereoacuity, ocular alignment/movement, refraction and ocular finding) of 5-year-old boy who presented with left intermittent ET which converted to a 48-hour cyclic ET over a 15-month period and its response to BTX treatment over a follow up period of 14 months.

Results: At presentation, in May 2021 his VA was 6/6 with either eye, he had left small esotropia (not cooperative for measurements), stereoacuity  400", normal ocular findings and refraction <+1Ds in each eye. ET was noticed only when he was tired. Over the next 12 months the frequency and duration of manifest ET increased from minutes to 24 hours, and became cyclic ET with a 48-hour cycle. His Left/Alternating ET was between 16-50^, with 0-10^ difference between near (N) and distance (D). He underwent bilateral medial rectus muscle BTX injection in Nov 2022. He remained esophoric for 2 months (12-16^) and then manifest Left ET reoccurred. Over the next 14 months, the duration of manifest ET was variable (10min- 24 hours) and the cycles extended (3 to 30 days). His ET was recorded between 30-45^.  In Dec 2023 his ET changed to 70^D and 90^N. In Jan 2024, on his 'straight' day, he had Left ET, 12^D, and 20^N, VA 6/6 right eye, 6/7.5 left eye and left eye suppression but still variable motor fusion. 

Conclusion: Cyclic ET is a poorly understood condition and the literature regarding its management is scarce. Classical treatment is extraocular muscle surgery targeting the largest angle of deviation and BTX has been proposed as an alternative. We present a case where we observed the onset of cyclic ET and its course after BTX treatment (change in size of ET, change of duration of deviation as well as its cycle).