Patient Information
Fourteen patients with secondary large-angle exotropia following medial rectus (MR) transection were retrospectively reviewed. The patients included 10 individuals who developed exotropia after endoscopic sinus surgery (ESS) and 4 who developed exotropia after orbital tumor resection (OTR). The mean age of patients was 40.2 years. All patients presented with significant exotropia characterized by outward deviation of the affected eye, associated diplopia in the primary gaze position, and limited ocular motility secondary to medial rectus muscle disruption.
Diagnosis
The key clinical finding was large-angle exotropia ranging from 50 to 100 prism diopters (PD). This was confirmed by standard ocular alignment assessment using prism cover testing. The diagnosis of secondary exotropia was attributed to transection of the medial rectus muscle during prior orbital or sinus surgery, as documented in the patient history and surgical records. This resulted in medial rectus palsy or absence of medial rectus function, leading to unopposed lateral rectus muscle action and large-angle exotropia. Diplopia was present in the primary gaze position, consistent with disrupted binocular single vision.
Differential Diagnosis
Differential considerations included:
– Cranial nerve III palsy: usually involves additional features such as ptosis and pupillary involvement unlike isolated medial rectus transection.
– Congenital or acquired restrictive strabismus: less likely given clear temporal relationship to surgery and muscle transection.
– Thyroid eye disease: typically involves proptosis and other muscle restrictions.
These were ruled out based on clinical presentation, imaging, and surgical history.
Treatment and Management
All patients underwent nasal vertical rectus belly transposition (VRBT) combined with a large lateral rectus recession. The nasal belly of the vertical rectus muscles (superior and inferior rectus) was transposed nasally to compensate for the absent medial rectus muscle pull. This procedure repositions the force vector of the vertical rectus muscles to both assist adduction and reduce exotropia. Additionally, a large recession of the lateral rectus muscle, with a mean amount of 10.9 mm, was performed to weaken its abduction force.
The decision to combine these two muscle surgeries was made to address the severe exotropia that often exceeds the effect of single-muscle surgery. Postoperative follow-up included assessment of ocular alignment at 1 month and at final follow-up, which averaged 26.3 months.
Outcome and Prognosis
Surgical results showed significant improvement in ocular alignment. Mean exotropia decreased from 70.7 ± 15.4 PD preoperatively to 9.8 ± 10.5 PD at 1 month postoperatively and 13.9 ± 13.1 PD at final follow-up (p < 0.001 for both). There was an average exotropic drift of 4.1 PD over time (range -5 to 15 PD, p = 0.016). Surgical success, defined as postoperative deviation within 10 PD, was achieved in 57% of patients.
When comparing the etiologies, the ESS group showed better outcomes with a mean exotropia correction of 60.0 ± 16.8 PD versus 45.0 ± 5.0 PD in the OTR group (p = 0.031). The ESS group also had less clinically significant residual exotropia (10% versus 75%, p = 0.041) and less exotropic drift (-2.3 PD versus -8.8 PD, p = 0.048). Diplopia in the primary position resolved in 79% of patients, and 50% regained stereopsis. No serious complications, such as globe perforation or significant motility limitations, were reported.
Discussion
This case series demonstrates that nasal vertical rectus belly transposition combined with lateral rectus recession is a safe and effective surgical approach for large-angle secondary exotropia caused by medial rectus transection. The technique addresses the significant muscle imbalance by augmenting adduction force through vertical rectus transposition and simultaneously weakening the abductor lateral rectus muscle.
The etiology of the medial rectus damage influenced outcomes, with patients who developed exotropia after endoscopic sinus surgery achieving better alignment results than those with orbital tumor resection. This may reflect differences in orbital tissue scarring, muscle integrity, or trauma severity impacting surgical response.
The mean exotropic drift observed emphasizes the importance of long-term follow-up as some degree of recurrent exotropia may develop, necessitating potential additional intervention. However, the majority of patients had favorable binocular outcomes including resolution of diplopia and partial stereopsis recovery.
This study adds to the growing evidence that vertical rectus transposition techniques, including nasal belly transposition variations, can effectively restore ocular alignment in complex strabismus cases where the medial rectus muscle is nonfunctional or absent. It underscores the need for tailored surgical planning based on etiology and degree of deviation.
References
1. Xia W, Jiang C, Ling L, Yao J, Zhao C. Outcomes of nasal vertical rectus belly transposition and lateral rectus recession for large exotropia after medial rectus transection. American Journal of Ophthalmology. 2026 Jul 14; PMID:42448083.
2. Scott AB, Devens EB. Vertical rectus transposition in the management of paralytic strabismus. Transactions of the American Ophthalmological Society. 1975;73:468-492.
3. Kushner BJ. Vertical rectus muscle transposition for large-angle esotropia and exotropia. Journal of Pediatric Ophthalmology and Strabismus. 1995;32(4):217-225.
