Resection and anterior transposition of the inferior oblique muscle for treatment of inferior rectus muscle hypoplasia with esotropia

Congenital anomalies of inferior rectus and its surgical outcomes

Congenital inferior rectus hypoplasia and aplasia is a rare abnormality of the extraocular muscles, and it is the second most common after superior oblique muscle aplasia. It has been reported either in isolation or with coexisting ocular or systemic associations. We describe here cases of inferior rectus hypoplasia/aplasia, their clinical features, and surgical approach to achieve satisfactory outcomes. We retrospectively reviewed medical records from January 2009 to December 2020 of patients with vertical strabismus due to inferior rectus hypoplasia/aplasia at a tertiary eye care center. Those who underwent surgical intervention with an adequate follow up postoperatively were included in the study. Three patients who presented with congenital hypertropia and diagnosed of inferior rectus aplasia/hypoplasia and who underwent strabismus surgery were identified. Diagnosis was based on clinical examination and orbital imaging. Coexisting horizontal deviation was present in two patients. None of the patients had any other ocular, cranial, or systemic anomalies. All patients had isolated inferior aplasia/hypoplasia with normal other extraocular muscles on orbital imaging. Intraoperatively, ipsilateral superior rectus was tight in all patients. All underwent ipsilateral superior rectus recession, whereas two patients with large vertical strabismus required additional inferior oblique anteronasal transposition in the same eye. Satisfactory outcomes were achieved in all three patients without the need for resurgery. Moderate to large vertical A pattern strabismus and limitation of infraduction are common clinical findings. Orbital imaging helps not only in diagnosis but also in surgical planning. Weakening of antagonist superior rectus with anteronasal transposition of inferior oblique not only gives good surgical outcomes but also avoids potential complications related to vertical transposition of either horizontal rectus muscle.

Clinical characteristics and surgical outcomes of isolated inferior rectus palsy

Aim

As isolated inferior rectus muscle (IRM) palsy represents a rare clinical entity, very limited information is available on this condition. The aim of this report was to elucidate the etiology, clinical characteristics and surgical outcomes of isolated IRM palsy.

Methods

Isolated IRM palsy cases who underwent surgical treatments at the Zhongshan Ophthalmic Center, Sun Yat-sen University, China over the period from January 2008 to June 2019 were reviewed retrospectively. Data evaluated from these cases included their etiology, ocular alignment, ocular motility, surgical procedures and surgical outcomes.

Results

A total of 61 patients (40 males, 21 females) were included in this review. Their mean ± SD age was 27.21 ± 16.03 years (range: 2 to 73 years). In these cases, 32 (52.5%) involved traumatic injury, 28 (45.9%) congenital hypoplasia or absence of inferior rectus and 1 (1.6%) with thyroid ophthalmopathy. The right eye was affected in 33 patients (54.1%), the left in 24 patients (39.3%), and both eyes in 4 patients (6.6%). The main clinical presentations consisted of hypertropia of the affected eye, motility limitation in abduction and depression and incyclotropia. After treatment consisting of various surgical approaches, including muscle repair or resection of the affected inferior rectus, recession of ipsilateral superior rectus, elongation of contralateral superior oblique and partial transposition of the horizontal rectus, the isolated IRM palsy was rectified in 49 patients (80.4%) with one surgery, while 11 cases (18.0%) required two surgeries and 1 case (1.6%) needed three surgeries. Finally, 52 patients (85.2%) showed a complete recovery, 6 (9.9%) improved and 3 (4.9%) experienced a surgical failure.

Conclusion

The main etiologies of isolated IRM palsy involved traumatic injury and developmental events. Overall, surgical outcomes of the various approaches employed were quite effective.

Clinical and imaging features of congenital and acquired isolated inferior rectus muscle hypofunction

BACKGROUND

Inferior rectus (IR) underaction may arise from various causes that are distinguishable through imaging. We investigated clinical and imaging characteristics of congenital and acquired causes of IR underaction.

METHODS

Cases of IR underaction were selected from data prospectively collected in a study of orbital imaging in strabismic patients.

RESULTS

Review identified 3 cases of congenital IR underaction (2 with bilateral IR aplasia and 1 with unilateral IR hypoplasia), 12 acquired cases, including 4 due to denervation (2 idiopathic, 1 after multiple strabismus surgeries, 1 after head trauma), and 8 cases of direct IR damage (5 with orbital trauma and 3 with previous surgery, including 2 sinus surgery and 1 laser blepharoplasty). Of the 23 cases, 11 adults had high-resolution magnetic resonance imaging, and 2 children had computed tomography. Imaging identified the anatomic diagnosis in congenital cases; in acquired cases, imaging helped to identify atrophy and exclude alternative orbital causes; and in direct mechanical damage, imaging clarified the mechanism of underaction, extent of IR damaged, and the degree of retained contractility. Patients with congenital IR absence or hypoplasia exhibited A pattern exotropia that was typically absent in isolated acquired denervation or direct IR damage.

CONCLUSIONS

Orbital imaging demonstrates a variety of abnormalities in patients with congenital or acquired IR hypofunction, helping to clarify the underlying mechanism and guide management.