Importance: Isolated medial rectus palsy is extremely rare in clinical practice.
Background: To report demographics, aetiology, clinical findings, imaging features and surgical outcomes in patients with isolated medial rectus palsy.
Design: Retrospective study.
Participants: All patients treated for isolated medial rectus palsy at Zhongshan Ophthalmic Center, Sun Yat-sen University, between September 2003 and March 2019.
Methods: Review of patient records.
Main outcome measures: Aetiology, clinical findings, imaging features and surgical outcomes.
Results: A total of 32 patients (22 males, 10 females) were included. Mean age was 33.19 ± 19.78 years. The right eye was involved in 17 patients, the left eye was involved in 14 patients, and both eyes were involved in one patient. The most common causes were iatrogenic injury (43.75%), followed by trauma (37.50%) and congenital (18.75%). The most common clinical findings included outward deviation, diplopia and limited adduction. Six patients showed combined small-angle vertical strabismus, and 10 patients experienced a scale of -1 motility defect in other directions. After individualized strabismus surgery, preoperative exotropia of 60 ± 25 prism diopters (PD) was significantly reduced to 12 ± 13 PD (t = 10.938, P < .0001). Ocular motility improved in 21 patients, and five patients achieved normal ocular motility. Successful correction was obtained in 20/32 (62.50%) patients, with under-correction in 12/32 (37.50%) patients. Twenty-eight patients had only one surgery, three patients had two surgeries and one patient had three surgeries.
Conclusions and relevance: The most common cause of isolated medial rectus palsy was local injury. Satisfactory results were obtained after individualized surgical interventions based on personalized preoperative evaluations.
Keywords: exotropia; imaging feature; isolated medial rectus palsy; orbit; strabismus surgery.
© 2020 Royal Australian and New Zealand College of Ophthalmologists.