The orbit includes the globe and the retrobulbar space, the retrobulbar space contains six extraocular muscles (EOMs): superior, inferior, medial, and lateral recti, as well as the superior and inferior oblique muscles. These muscles work in coordination to control movements of the eyeball and eyelids. These muscles are an important reference point for strabismus surgery. (1) Intraorbital structures -including the EOMs- can be affected by variety of acquired local and systemic diseases including neurological, metabolic, infiltrative, endocrine such as Graves’ disease and traumatic causes. (2)

Ocular motility disorders are relatively common and may be a significant source of discomfort and morbidity. Although the presence of restricted eye movement can be detected clinically, determining the underlying cause of ocular dysmotility often requires imaging evaluation. Imaging plays a crucial role in excluding and detecting a specific cause responsible for the clinical presentation. However, the radiologist should be aware that the imaging findings in many of these conditions when taken in isolation from the clinical history and symptoms are often nonspecific. (3) In such cases, it is necessary to evaluate the changes in orbital structures carefully to investigate the severity of the disease, to plan the treatment correctly, to predict the postoperative outcome, and also to evaluate the response to the treatment. (4)

Thyroid disease is a multifactorial disease affecting orbital structures such as adipose tissue and extraocular muscle with inflammatory changes that can cause disfiguring and sight-threatening injuries. (5) Patients may experience as exophthalmos, eyelid retraction, lateral flare, strabismus, and optic neuropathy. (6)

Although the diagnosis of Graves ophthalmopathy (GO) is based on clinical findings, imaging exams, including magnetic resonance imaging (MRI), computed tomography (CT), and ultrasonography can add valuable information on tissue microstructure, leading to new findings on actual disease progress and status, which is vital for planning treatment and interventions. (7)

Imaging in patients with GO may reveal an increase in orbital fibroadipose tissue, enlargement of extraocular muscles, and optic-nerve compression. Imaging is especially warranted in cases of asymmetric proptosis and for differential diagnosis. (8)

Extraocular muscle enlargement is the most common sign among these patients, usually affecting younger and older patients differently. The inferior rectus muscle is the most frequently involved in clinical myopathy, followed by medial, superior, and lateral rectus muscles, respectively. In GO, multiple muscles can be involved simultaneously and/or bilaterally in 76% to 90% of the cases. (9)

According to Su et al., younger patients are less affected by motility restriction despite developing more proptosis even with enlarged muscles, whereas older patients suffer from more motility restriction and diplopia due to the muscle bellies enlargement posterior in the orbit. Proptosis is mainly related to the most enlarged muscle position than the size itself. (10)

Diagnosis is based on patient’s history, clinical manifestations, and typical features on computed tomography or magnetic resonance imaging. The appearance of the tendonous muscle insertion on the globe seen with neuroimaging may help distinguish idiopathic orbital inflammatory syndrome (IOIS) from the muscle enlargement of orbital Grave's disease: thickened, involved tendons with IOIS; thin, normal-appearing tendons with orbital Graves disease (although they do sometimes enhance). (11)

Orbital fractures are typically the result of middle third facial traumas. Blow out fractures are usually associated with injuries to surrounding soft tissues and orbital cavity contents. They may cause entrapment or herniation of orbital fat and extraocular muscles, resulting in limited eye movements and/or enophthalmos due to intra-orbital volume reduction. The inferior orbital wall is the most commonly involved site, followed by the medial orbital wall. (12)

CT represents the gold standard for investigating suspected orbital fractures and identifying foreign bodies, due to the excellent bone and soft-tissue visualization. CT is a quick and widely available imaging modality. Thanks to the possibility of multiplanar and tridimensional reconstructions, CT is also the primary imaging modality for surgical planning of fracture reconstructions and treatment management. (12)

Direct EOM involvement can range from mild: minimal displacement from adjacent soft tissue edema or hemorrhage; to moderate: contusion of the EOM itself; to severe: disinsertion, laceration, or incarceration of the EOM from the traumatic blow or by an orbital fracture. Indirectly, EOM motility may be impaired from cranial nerve palsy or supranuclear injury associated with head and neck trauma. The goal of EOM management during acute ocular or orbital surgery is to limit the amount of fibrosis that could occur and result in strabismus. (13)

EOM entrapment or flap tears may follow orbital fractures, which comprise the most common cause of traumatic strabismus. The resultant strabismus depends on the fracture location and extent of EOM involvement. (13)

Bony fragments can impinge surrounding EOMs, commonly the inferior rectus, inferior oblique, and medial rectus, and less commonly, the superior oblique. (14)

The aim of this study to characterize and categorize the spectrum of CT findings in some acquired adult non-neuromyopathic ocular dysmotility caused by both traumatic and non-traumatic extra-ocular muscle afflictions, providing a practical imaging framework for radiologists and referring clinicians. We meant to include the uncommon traumatic, degenerative, metabolic and idiopathic causes which are uncommonly discussed in radiology literature and uncommonly afflict the EOMs to cause strabismus. We meant to exclude the more common neuro-muscular disorders discussed on MRI basis.

included adult patients (> 16 years) with clinical diagnosis of limitation of ocular movement due to extra-ocular muscle (EOM) pathology which detected on CT.

Patients with congenital, neuromyopathic, or neurogenic causes of ocular dysmotility were excluded.

Based on clinical and imaging data, patients were categorized into two main groups: traumatic and non-traumatic causes.

All patients underwent non contrast multidetector CT scan of the orbits using a [……]. Scans were obtained in both axial and coronal planes, with thin-section (0.5–1 mm) reconstructions.

Tube voltage: 120 kVp, Tube current: 150–250 mAs (automatically adjusted), Matrix size: 512 × 512, Field of view: tailored to the orbit

Multiplanar reconstruction and 3D reformat were used for better evaluation of extra ocular muscles involvement and adjacent orbital structures and paranasal sinuses.

This study included 40 patients and consisted predominantly of males (70%), with a mean age of ~ 30 years (range 16–50). Table 1

According to presentation, Left-sided strabismus and myopic strabismus fixus accounted for more than half of presentations (30% and 22.5%, respectively) (Fig. 1). Most patients had a slow onset of diplopia (70%) and long-standing disease (70%). By etiology, blunt orbital trauma was the most common cause (52.5%) (Fig. 2). While myopia-related disorders (22.5%) (Fig. 4) and isolated idiopathic cases (20%) (Fig. 1) comprised the majority of non-traumatic etiologies. Only two patients (5%) had thyroid ophthalmopathy (Fig. 5), and hyperthyroidism was the only recorded systemic comorbidity. Table 2

In more than half of patients (52.5%), muscle involvement was left-sided while bilateral in 20%. The inferior rectus and superior oblique muscles were the most frequently affected EOMs (27.5% each), followed by the medial rectus (22.5%) (Figs. 1–3). CT findings demonstrated thinning or atrophy (50%), with detachment/disinsertion in (22.5%) and full-thickness tears in (7.5%). Nearly 40% of patients had no additional orbital abnormalities; when present, blow-out floor fractures (15%) predominated. (Fig. 2) Table 3

No fracture was found in 77.5% of cases. when present, inferior or medial wall blow-out fractures was found to be accounted for 7.5% for each (Fig. 2). According to muscle tears, extra-ocular muscle tear was confirmed by CT in nine patients (22.5%), two-thirds of which were full-thickness (Figs. 2 and 3). The optic nerve was intact in all cases. Adjacent sinusitis was present in 27.5% of cases. Table 4

In the present study, majority were young males (mean age ~ 30 years, 70% male), and the trauma was slightly more common (52.5%) than non-traumatic causes (47.5%), with blunt orbital trauma dominating the traumatic category, reflecting the higher risk of trauma in this group.

Parallel to our results, Li et al. ^[15] found that eye injuries disproportionately affect young/ middle ages males, with largely unintentional mechanisms (sports/occupational/transport). Also, Bineshfar et al. ^[16] included 49,765 cases; 79% male; mean age 27 ± 19 y. Sports implicated in such injuries included baseball, bicycling, and softball, all consistent with high-energy orbital impacts that can entrap or injure extraocular muscles (EOMs). Furthermore, Wee et al. ^[17] in a Korean series found that cases with muscle entrapment skewed younger (median 17 y) compared with all blow-outs (mean 34 y), reinforcing that EOM-related dysmotility after trauma clusters in younger patients. Another study by Chen et al. ^[18] found that among 36 patients with traumatic or iatrogenic EOM ruptures, two-thirds were male and the mean age was 34 y. In an Egyptian cases series, Soliman and Macky ^[19] reported marked male predominance among ocular trauma admissions.

Our study included 6 cases of blow out floor and 3 of blow out medial wall, which is matching with agreed on by literature that weakest orbital wall is floor followed by medial wall, both can yield under pressure created by blow out. A case had combined walls comminuted blow out. Patients with post-blow out strabismus are those suffering significant EOM entrapment into fracture site, and only included in our study.

Parallel to these results, Lee et al. ^[20] found that in patients with orbital wall fractures, up to 100% had ocular motility disturbance, and 89–98% experienced diplopia, indicating that blunt orbital trauma is a potent cause of EOM dysfunction. Also, Goelz et al. ^[21] found that orbital injuries were confirmed in 23.6% of patients with facial injuries, and soft tissue involvement—including muscle displacement—was frequent (e.g., 44.6% showed EOM displacement). This underlines the prominent role of trauma in EOM-related pathologies. The entrapped muscle looks deviated and pulled into site of fracture with thickening and hypertrophy of its flesh created by traction.

Strabismus associated with high myopia was the leading non-traumatic cause. This is coined specific terms as myopia-associated strabismus (“heavy eye syndrome”). Disease is usually bilateral and in middle age (Female > Male), and still can occur unilaterally and in older or younger ages. Our study included 9 cases of myopic strabismic fixus: 6 females: 3 males, 6 bilateral.

In agreement with our data, Su et al. ^[22] found that myopia-associated strabismus (“heavy eye syndrome”) is a rare but significant non-traumatic cause of ocular motility disturbance, resulting from high myopia-associated globe elongation causing muscle displacement and motility restriction. Quite similar, a large European hospital study by Kooger et al. ^[23] found that non-traumatic ophthalmic conditions (e.g., endocrine or myopic changes) often accounted for a substantial number of ocular motility consultations.

Similar to our results, a Level I trauma center series by Chiang et al.^[24] found left orbital fractures significantly more common than right, reinforcing a left-sided trend. Kooger et al.^[23] likewise reported left-sided fractures in 50.5% vs 44% right and documented bilateral cases (5.5%), underscoring that while laterality skews left, bilateral involvement does occur. Complementing these epidemiologic signals, an imaging-mechanistic review by Cellina et al.^[12] showed that blow-out fractures frequently involve the orbital floor with lateral or medial wall extension, a pattern that helps explain how typical impact vectors and bony weak points can yield apparent lateral preferences on CT.

Regarding incidence of EOMs involvement in the uncommon etiopathologies resulting in ocular dysmotility: the inferior rectus, superior oblique, and medial rectus were the most commonly affected muscles, with thinning/atrophy being the dominant morphological pattern (50%). The inferior rectus showed highest prevalence of affection (n = 11) being entrapped into a complex blow out, assuming a hypertrophied morphology and deviated direction towards fracture site and 3 cases had complete full thickness flap tear. Lateral rectus showed bilateral involvement in heavy eye syndrome (n = 6) appearing thinned stretched along with nasal displacement of superior rectus (SRs). Medial rectus showed high prevalence too (n = 9), being entrapped in medial wall blow out in 3 cases, remaining involved in traumatic disinsertion and post traumatic atrophy. Superior oblique muscle was involved in isolated atrophy in (n = 11) (assumed to be following remote eye surgery due to prolonged displacement and compression) by traction techniques, and sometimes no cause identified, while degenerative calcifications of trochlea was also seen in 2 cases, correlated with limited movement and strabismus not a mere incidental senile finding. The inferior rectus also showed predominant involvement in thyroid-associated orbitopathy being most commonly affected muscle.

Anatomical background can explain variable incidence and involvement of EOMs in pathologies. The inferior rectus lies adjacent to the orbital floor and is prone to entrapment or compression in blow-out fractures; the medial rectus is similarly vulnerable in medial wall injuries; while the superior oblique’s involvement may reflect its role in torsional movement and its susceptibility when orbital support structures are disrupted. The high incidence of thinning or atrophy suggests chronic muscle compromise resulting in volume loss rather than acute swelling, with example exist following prolonged eye surgeries, where medially located EOMs, are tracked for long time resulting in vascular compromise and postulated delayed atrophy ^[13].

In harmony with these data, Tomasetti et al. ^[25] document an isolated inferior rectus rupture after blunt trauma and noted that the inferior and medial recti muscles are most often involved because of their exposed course and limited protective buttressing. Cellina et al. ^[12] further show on computerized tomography (CT) that orbital floor fractures commonly displace or herniate the inferior rectus into the maxillary sinus, underscoring its high susceptibility in trauma. Extending this pattern beyond trauma, Fidor-Mikita and Krupski ^[26] demonstrate that in dysthyroid ophthalmopathy the inferior (61%) and medial rectus (54%) are the most frequently enlarged on CT, indicating that similar anatomical and functional predispositions also drive involvement in non-traumatic disease. In contrast, Chen et al. ^[18] reviewing isolated EOM ruptures, found superior oblique involvement to be rare (1 patient).

In the current study, multi-slice CT (MSCT) effectively demonstrated fracture lines (22.5% of cases), muscle tears (22.5%), and fat entrapment (15%), highlighting its role in evaluating post-traumatic orbital pathology. CT effectively reveals bony disruptions, delineates soft-tissue involvement such as extra-ocular muscle tears or displacement, and detects orbital fat herniation or entrapment into adjacent sinuses. ^[27].

In accordance, Cellina et al. ^[12] showed that CT consistently demonstrates orbital wall fractures with associated soft-tissue herniation (muscle or fat) and can depict globe/nerve injury when present, establishing CT as the first-line map of injury patterns in traumatic emergencies. Also, Folkestad et al. ^[28] found that the rounding sign of the inferior rectus on CT correlated with soft-tissue herniation and diplopia, underscoring CT’s value for identifying muscle involvement and fat prolapse and for surgical planning. Similarly, Chiang et al. ^[29] linked CT-detected entrapment (13%) with clinical diplopia (13%) and motility restriction (17%), highlighting CT’s sensitivity for clinically meaningful muscle compromise. In contrast, Lin et al. ^[30] reported that while CT exceeds 70% sensitivity for entrapment, it is less sensitive for muscle lacerations or intramuscular injuries, implying potential under-detection on CT alone; and Migliorini et al. ^[31] showed that ocular motility testing may reveal entrapment even when CT appears negative, arguing for integrated imaging–clinical algorithms and selective surgical exploration.

In the present study, hypertrophy/enlargement was the key finding in thyroid ophthalmopathy, while myopic strabismus fixus cases showed elongated or displaced muscles with globe enlargement: These patients had bulky elongated eye globes changing their directions to be in clos opposition to walls, with consequent dynamic changes of the EOMs in response to this directional change of eye globe, mainly infero-laterally. The lateral rectus appears thinned and stretched in shape and directed inferolateral stuck in between lateral wall and globe. The superior rectus tend to show nasal/medial displacement and appears thickened as compensatory response.

In non-traumatic cases, thyroid ophthalmopathy manifested predominantly as extraocular muscle hypertrophy/enlargement, reflecting autoimmune-mediated inflammation and fibrotic remodeling ^[32]. Contrastingly, myopic strabismus fixus cases displayed distinctive muscle displacement patterns—typically inferior displacement of the lateral rectus and nasal shift of the superior rectus—accompanied by globe elongation and proptosis ^[22].

In accordance, Fidor-Mikita and Krupski ^[26] showed the hallmark fusiform, tendon-sparing enlargement of extraocular muscles—predominantly the inferior and medial rectus—with accompanying orbital fat expansion, proptosis, and apex crowding. Also, Xiong et al. ^[33] used 3D-based CT volumetry to confirm significant increases in both EOM and orbital fat volumes in Thyroid-Associated Orbitopathy (TAO). In addition, Kaur et al. ^[34] detailed classic myopic strabismus fixus CT signs—nasalized superior rectus and inferiorly displaced lateral rectus in elongated globes. Contrastingly, Enzmann et al. ^[35] CT work in Graves’ ophthalmopathy corroborates muscle enlargement but lacks today’s resolution and does not delineate modern displacement mechanics; and an MRI-based Case Reports by Gatt et al. ^[36] descriped heavy-eye syndrome emphasizing LR–SR band thinning and superotemporal globe displacement.

This study highlights the CT spectrum of acquired non-neuromyopathic ocular dysmotility in adults resulting from traumatic and non-traumatic extra-ocular muscle (EOM) etiologies. Trauma— predominantly blunt orbital injury—was slightly more frequent than non-traumatic causes, particularly in young males, highlighting the demographic vulnerability of this group with inferior and medial rectus muscles were the most commonly affected, reflecting their anatomic exposure along the orbital floor and medial wall.

CT was highly effective in detecting the main morphological changes, such as fracture lies, associated fat entrapment and sinus disease as well as muscle tear, entrapment, disinsertion, thinning or atrophy. In non-traumatic etiologies, CT identified characteristic hypertrophy in thyroid ophthalmopathy and elongation or displacement in high-myopia–related strabismus fixus.

Preserved optic nerves across all cases of this study emphasize that dysmotility in this cohort was primarily arising from extraocular muscles rather than neurogenic or optic nerve injury.

Overall, CT provides a non-invasive, available, rapid, and comprehensive tool for evaluating causes and extent of ocular dysmotility, guiding diagnosis, and surgical planning and follow up.