The purpose of this case report is to report a case of congenital idiopathic enlargement of extraocular muscles. A four-month-old girl showed limitation of adduction and supraduction in the right eye. A computerized axial tomography (CAT) scan revealed hypertrophy of the lateral rectus muscle and inferior rectus muscle of the right eye. Thyroid hormone and antibody levels were normal. No inflammatory findings on magnetic resonance imaging (MRI). A traction test under general anesthesia revealed a strong limitation of supraduction and a mild limitation of adduction. Therefore, the inferior rectus muscle was recessed 4.5 mm at the age of six months. A partial biopsy of the inferior rectus showed no inflammatory cell infiltration. After the first surgery, the patient\'s limitation of supraduction improved, but the limitation of adduction persisted. So, a 5 mm recession of the right lateral rectus muscle was added at one year and one month. However, the hypertropia of the sound eye became stronger after treatment of amblyopia. Because of the strong limitation of supraduction, tenotomy of the inferior rectus was performed at the age of six years. Postoperatively, no impairment of infraduction occurred, and the limitation of supraduction was mildly improved. Since the findings on MRI were not changed through our observation period, we concluded that the patient had idiopathic external ophthalmoplegia.

The extraocular muscles (EOMs) possess unique characteristics that set them apart from other skeletal muscles. These muscles, responsible for eye movements, exhibit remarkable resistance to various muscular dystrophies and aging, presenting a significant contrast to the vulnerability of skeletal muscles to these conditions. In this review, we delve into the cellular and molecular underpinnings of the distinct properties of EOMs. We explore their structural complexity, highlighting differences in fiber types, innervation patterns, and developmental origins. Notably, EOM fibers express a diverse array of myosin heavy-chain isoforms, retaining embryonic forms into adulthood. Moreover, their motor innervation is characterized by a high ratio of nerve fibers to muscle fibers and the presence of unique neuromuscular junctions. These features contribute to the specialized functions of EOMs, including rapid and precise eye movements. Understanding the mechanisms behind the resilience of EOMs to disease and aging may offer insights into potential therapeutic strategies for treating muscular dystrophies and myopathies affecting other skeletal muscles.

OBJECTIVE: Small angle hypertropia in sagging eye syndrome is conveniently treated by graded vertical rectus tenotomy, yet an adjustable technique under topical anesthesia has been recommended because of variability of effect. We performed graded tenotomy in an experimental model to elucidate the reason for variability of response to this surgical procedure.
METHODS: Experimental study.
METHODS: Thirty-two fresh bovine rectus musculotendon specimens were prepared including continuity with insertional sclera, and extending for a total 40 mm length to the proximal muscle bellies, and trimmed to 16 mm width. Specimens were anchored by the clamps at the scleral insertion and muscle belly ends within a physiological chamber. After preconditioning and elongation to 10% strain was imposed by a linear motor, tensile force was allowed to stabilize at a plateau state. Then 25%, 50%, 75%, 90%, and 100% marginal tenotomies were performed progressively as remnant forces were measured.
RESULTS: Tendon thickness averaged 0.29 ± 0.05 mm and width 19.71 ± 2.25 mm. On average, remnant force decreased linearly (R2 = 0.985) from 4.23 ± 1.34, 2.76 ± 0.88, 1.70 ± 0.73, 1.01 ± 0.49, 0.39 ± 0.10, and 0 N, at 0%, 25%, 50%, 75%, 90%, and 100% tenotomy. However, there was marked individual variability in effect among specimens, with coefficients of variation of 32%, 32%, 43%, 49%, and 27%, respectively.
CONCLUSIONS: On average, there is a linear relationship between graded rectus tenotomy and percentage force reduction, but the effect among individual tendons is large, paralleling the reported variation in surgical effect. This explains and implies continued advisability of adjustable technique in this procedure.

OBJECTIVE: To investigate the alterations in extraocular muscles (EOMs) by magnetic resonance imaging (MRI) among patients diagnosed with Duane retraction yndrome (DRS) and congenital fibrosis of the extraocular muscles (CFEOM), who present with various cranial nerve anomalies in an attempt to enhance the clinical diagnostic process.
METHODS: A case-control study was conducted to evaluate 27 patients with DRS and 14 patients with CFEOM. All patients underwent MRI scans of the brainstem and orbital examination. Neurodevelopmental assessments were conducted through MRI, and maximum cross-sectional area and volumes of EOMs were obtained. Three types of models were constructed using machine learning decision tree algorithms based on EOMs to predict disease diagnosis, cranial nerve abnormalities, and clinical subtypes.
RESULTS: Patients with bilateral CN VI abnormalities had smaller volumes of LR, MR, and IR muscles compared to those with unilateral involvement (P < 0.05). Similarly, patients with CFEOM and unilateral third cranial nerve abnormalities had a smaller maximum cross-section of the affected eye\'s SR compared to the contralateral eye (P < 0.05). In patients with both CN III and CN VI abnormalities, the volume of SR was smaller than in patients with CN III abnormalities alone (P < 0.05). The prediction model using EOMs volume showed a diagnostic precision of 82.5% for clinical cases and 60.1% for predicting cranial nerve abnormalities. Nonetheless, the precision for identifying clinical subtypes was relatively modest, at only 41.7%.
CONCLUSIONS: The distinctive volumetric alterations in EOMs among individuals exhibiting distinct cranial nerve anomalies associated with DRS or CFEOM provide valuable diagnostic insights into to Congenital Cranial Neurodevelopmental Disorders (CCDDs). MRI analysis of EOMs should thus be regarded as a crucial diagnostic modality.

OBJECTIVE: Extraocular muscles have complex development processes. The present study aimed to analyze the presence of myosin, dystrophin, and collagen IV in the strabismus-affected extraocular muscle.
METHODS: This research was an observational case-control study. Myosin, dystrophin, and collagen IV were detected by histological and immunohistochemical analyses of extraocular muscle samples from concomitant strabismus patients and controls. A semi-quantitative grading method and statistical analysis were used.
RESULTS: In the strabismus-affected extraocular muscle, morphological analysis demonstrated different-sized muscle fibers. Immature muscle fibers and an increased amount of connective tissue were also noted. Strong positive correlations were identified between myosin and collagen IV and between dystrophin and collagen IV.
CONCLUSIONS: The presence of newly formed muscle fibers, increased connective tissue, and variable diameters of skeletal striated muscle fibers indicate the decreased quality of extraocular muscles in strabismus cases. Reduced levels of myosin and dystrophin and a near absence of collagen IV in strabismus-affected skeletal striated muscle fibers characterized the muscular dystrophy of strabismus. Adjuvant therapy aimed at normalizing the metabolism of these muscles may be appropriate alongside concomitant strabismus treatment.

UNASSIGNED: This study investigates the new combined parameters of 99mTc-DTPA orbital single-photon emission computed tomography/computed tomography (SPECT/CT) for the evaluation of Graves\' orbitopathy (GO) activity.
UNASSIGNED: A retrospective analysis was performed on 41 patients. All the patients undergone the 99mTc-DTPA orbital SPECT/CT and were categorized into active and inactive group based on the standard combined by the clinical active score (CAS), magnet resonance imaging (MRI) and/or follow-up results. Quantitative parameters of lacrimal gland (LG) including the protruding degree of lacrimal gland herniation (LGH) and uptake ratios (URs) of region of interest (ROI) drawn on lacrimal gland and occipital bone. SPECT/CT reading results were based on visual analysis. Parameters were compared between the two groups and the diagnostic value on discrimination of GO activity was also evaluated.
UNASSIGNED: All parameters of SPECT/CT for active GO groups were significantly higher than those of the inactive groups (p<.05). There were notable linear positive correlations between the assumption standard and readings as well as combination models 2 and 3 (r = .794, r = .772, r = .760, respectively). ROC analysis indicated that model 2 provided the highest diagnostic performance, exhibiting an area under the curve (AUC) of .947, a sensitivity of 92.7%, and a specificity of 88.6%.
UNASSIGNED: The combined use of SPECT/CT reading results and DTPA uptake parameters of LG offers a more objective and precise evaluation of active GO. This study further recommends 99mTc-DTPA SPECT/CT might be serving as a supplementary beneficial approach for CAS in evaluating GO activity.

UNASSIGNED: To determine which mechanisms are operative in releasing the extraocular myofascial tissue in response to extraocular myofascial release (EOMR) and to evaluate the effect of EOMR on saccadic velocity and esodeviation angle in patients with convergence spasm.
UNASSIGNED: Fourteen patients with convergence spasm aged 20-35 participated in this research. The treatment included touching the medial rectus and its interrelated fascial tissue with the index finger pulp from over the eyelid for at least 300 s and applying very gentle and uniform pressure. We evaluated the saccadic velocity obtained from dynamic electrooculography (EOG) and the angle of deviation. The findings of dynamic EOG were used as a reliable quantitative method to assess eye movement function.
UNASSIGNED: The amount of esodeviation decreased significantly at both far 2.39Δ, 95% confidence interval (CI) (1.27-3.52) (P = 0.002) and near 5.57Δ, 95% CI (4.67-6.47) (P = 0.001) after two sessions of EOMR in a week. There was no significant difference in saccadic velocities before and after treatment.
UNASSIGNED: In the short term, the EOMR only affects the static condition of the eye. Therefore, a significant improvement could be seen in the deviometric findings. However, the dynamic properties of the extraocular muscles did not improve and probably needed a more extended treatment period for acting the long-term mechanisms.

Skeletal muscle stem cells (MuSCs) are recognised as functionally heterogeneous. Cranial MuSCs are reported to have greater proliferative and regenerative capacity when compared with those in the limb. A comprehensive understanding of the mechanisms underlying this functional heterogeneity is lacking. Here, we have used clonal analysis, live imaging and single cell transcriptomic analysis to identify crucial features that distinguish extraocular muscle (EOM) from limb muscle stem cell populations. A MyogeninntdTom reporter showed that the increased proliferation capacity of EOM MuSCs correlates with deferred differentiation and lower expression of the myogenic commitment gene Myod. Unexpectedly, EOM MuSCs activated in vitro expressed a large array of extracellular matrix components typical of mesenchymal non-muscle cells. Computational analysis underscored a distinct co-regulatory module, which is absent in limb MuSCs, as driver of these features. The EOM transcription factor network, with Foxc1 as key player, appears to be hardwired to EOM identity as it persists during growth, disease and in vitro after several passages. Our findings shed light on how high-performing MuSCs regulate myogenic commitment by remodelling their local environment and adopting properties not generally associated with myogenic cells.

OBJECTIVE: To investigate the difference of medial rectus (MR) and lateral rectus (LR) between acute acquired concomitant esotropia (AACE) and the healthy controls (HCs) detected by magnetic resonance imaging (MRI).
METHODS: A case-control study. Eighteen subjects with AACE and eighteen HCs were enrolled. MRI scanning data were conducted in target-controlled central gaze with a 3-Tesla magnetic resonance scanner. Extraocular muscles (EOMs) were scanned in contiguous image planes 2-mm thick spanning the EOM origins to the globe equator. To form posterior partial volumes (PPVs), the LR and MR cross-sections in the image planes 8, 10, 12, and 14 mm posterior to the globe were summed and multiplied by the 2-mm slice thickness. The data were classified according to the right eye, left eye, dominant eye, and non-dominant eye, and the differences in mean cross-sectional area, maximum cross-sectional area, and PPVs of the MR and LR muscle in the AACE group and HCs group were compared under the above classifications respectively.
RESULTS: There were no significant differences between the two groups of demographic characteristics. The mean cross-sectional area of the LR muscle was significantly greater in the AACE group than that in the HCs group in the non-dominant eyes (P=0.028). The maximum cross-sectional area of the LR muscle both in the dominant and non-dominant eye of the AACE group was significantly greater than the HCs group (P=0.009, P=0.016). For the dominant eye, the PPVs of the LR muscle were significantly greater in the AACE than that in the HCs group (P=0.013), but not in the MR muscle (P=0.698).
CONCLUSIONS: The size and volume of muscles dominant eyes of AACE subjects change significantly to overcome binocular diplopia. The LR muscle become larger to compensate for the enhanced convergence in the AACE.

UNASSIGNED: Acute acquired concomitant esotropia induced by excessive digital device usage, especially smartphones (SAACE), has been increasing over the past few years. Convergence spasm induced by excessive near work has been suggested as a mechanism. Anatomical differences could also potentially contribute to SAACE onset. The present study investigated the conformation of horizontal recti between SAACE patients and normal subjects.
UNASSIGNED: In 15 SAACE patients (SAACE group), the distances between the limbus and insertion of the horizontal recti (LI distance) and the widths of horizontal recti on the insertion (insertion width) were measured. The control group consisted of 30 patients who underwent retinal detachment surgery. Differences in LI distances and insertion widths were compared between SAACE and control groups.
UNASSIGNED: While there were no differences between the two groups for LI distances and insertion widths of lateral recti, there were significantly shorter LI distances for the medial recti in the SAACE group (P<0.05). Moreover, the SAACE group tended to exhibit larger insertion widths of the medial recti. Medial/lateral ratio of LI distances were significantly lower and insertion widths were significantly higher in the SAACE compared to the control group (P<0.05).
UNASSIGNED: Based on the observations of more anterior insertion and larger muscle widths, this suggests there are stronger forces of medial recti in SAACE. In addition to excessive accommodation followed by increases in medial recti tonus, the results also suggest that an anatomical imbalance between lateral and medial recti contributes to esotropia onset following excessive near work.