To assess metrics of diffusion tensor imagining (DTI) in evaluating microstructural abnormalities of horizontal extraocular muscles (EOM) in esotropia.

Six adult concomitant esotropia patients, 5 unilateral abducent paralysis patients and 2 healthy volunteers were enrolled. Conventional magnetic resonance imaging (MRI) and DTI were performed on all subjects using 3T MR scanner. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) of medial and lateral rectus muscles were measured and compared between patients group and control group.

Medial rectus MD and RD within the adducted eye of concomitant patients was significantly greater than that in unilateral abducent paralysis patients (0.259×10^-2 mm²/s vs 0.207×10^-2 mm²/s, P=0.014; 0.182×10^-2 mm²/s vs 0.152×10^-2 mm²/s, P=0.017). Both strabismus patients showed a significantly decreased MD and AD than that obtained in normal controls for lateral rectus muscles (P<0.05). Medial rectus MD of the adducted eye in concomitant strabismus patients was significantly decreased than that in healthy controls (0.259×10^-2 mm²/s vs 0.266×10^-2 mm²/s, P=0.010). Lateral rectus AD of the adducted eye in concomitant strabismus patients was significantly decreased as compared with that in healthy controls (0.515×10^-2 mm²/s vs 0.593×10^-2 mm²/s, P=0.013). No statistically significant differences were present between the adducted and fixating eyes in concomitant strabismus patients.

DTI represents a feasible technique to assess tissue characteristics of EOM. The effects of eye position changes on DTI parameters are subtle. Decreased MD and RD could be evidence for remodeling of the medial rectus muscle contracture. Lower medial and lateral recuts MD of concomitant esotropia patients indicates a thinner fibrous structure of the EOM. Lower MD and AD should be general character of esotropia.

To describe the clinical manifestations, imaging features and surgical treatments in 5 cases of extraocular muscle (EOM) dysplasia presenting as orbital space-occupying lesions (SOL).

Records from the 5 cases with EOM dysplasia between 2004 and 2016 were retrospectively reviewed and clinical data were recorded including family history, age at onset, age at surgery, visual acuity, cycloplegic refraction, ocular alignment and motility, stereoacuity, exophthalmos, anterior segment and fundus, orbital computed tomography (CT) or magnetic resonance imaging (MRI) scan, surgical methods and final outcomes.

All 5 cases (1 male, 4 females) were unilateral (3 right, 2 left eyes). The average age was 5.4y (range 4-6y) with no family history. Patients had unilateral strabismus (horizontal and vertical), restricted eye movement, and eyelid changes (abnormal fissures, lagophthalmos, and/or entropion) in the affected eye. None had proptosis; 1 had 2-mm enophthalmos. Orbital CT/MRI showed irregular, ill-defined masses in EOM. Two anterior orbitotomies and 3 strabismus surgeries were performed, and pathology confirmed EOM dysplasia. After surgery, horizontal deviations, which ranged from exotropia (XT) 10 prism diopter (PD) to esotropia (ET) 10 PD (average 6 PD), decreased by an average of 18 PD, while vertical deviations, which ranged from 4 PD to 20 PD (mean 9.8 PD), decreased by an average of 23.2 PD.

SOL from EOM dysplasia is non-familial and typically presenting unilaterally characterized by an irregular, diffusely infiltrating mass within the EOM. EOM involvement causes strabismus, restricted eye movement, eyelid changes, and enophthalmos likely due to cicatricial processes.

To investigate the potential mechanisms of A-V pattern and evaluate the surgical outcomes used in the treatment of sensory exotropia.

The medical records of patients with sensory A-V pattern exotropia who underwent strabismus surgery between May 2014 to June 2019 was retrospectively reviewed. The control group included sensory exotropia patients without A-V pattern and concomitant A-V pattern exotropia patients with normal vision who undergone strabismus surgery over this same time period. Ocular alignment, best corrected visual acuity, oblique muscle function, and stereopsis records were collected.

Among the 843 eligible patients, 91 (10.79%; 39 males and 52 females) had A-pattern (54, 6.4%) or V-pattern (37, 4.4%). Age at onset of vision impairment was 4±5y and at the time of surgery was 25±9y. Statistically significant negative correlations were present between impaired visual acuity and the pre-operative exodeviation (r=-0.198, P=0.016) and patterns (r=-0.207, P=0.015). Age at surgery and exodeviation in patients with concomitant A-V pattern exotropia was significantly earlier as compared with that of sensory A-V pattern exotropia and sensory exotropia (both P<0.0001). There were no significant differences in these clinical variables between sensory exotropia with or without A-V pattern. Deviation and pattern were significantly reduced in patients receiving horizontal rectus surgery with or without oblique muscle surgery (both P<0.0001).

The prevalence of sensory A-V pattern exotropia in our study is 10.79%. Visual acuity represents an important factor contributing to the occurrence and development of A-V pattern. Isolated horizontal rectus surgery can provide a good option for the correction of sensory A-V pattern exotropia.