Diameter Of Extraocular Muscles Research Articles

Evaluation of the Normal Measurements of Orbital Structures in Healthy Adult Individuals by Using a Magnetic Resonance Imaging Method.

This study aims to determine the normal values of orbital structures according to sex in healthy adults. Diameters of extraocular muscles, the width of the optic nerve sheath diameter, the length of the inter-zygomatic line, ocular bulb length, and globe position were measured in the T1-weighed MR (magnetic resonance) images in 204 orbits of 102 individuals. The mean values of the diameters of the extraocular muscles in males and females were as follows: medial rectus, 3.96 ± 0.52 and 3.58 ± 0.53 mm; lateral rectus, 3.47 ± 0.61 and 3.15 ± 0.48 mm; inferior rectus, 4.47 ± 0.53 and 4.07 ± 0.48 mm; superior rectus, 4.44 ± 0.64 and 4.01 ± 0.56 mm; and superior oblique, 3.68 ± 0.49 and 3.45 ± 0.44 mm. The length of the interzygomatic line in males and females were 102.68 ± 3.89 and 96.95 ± 3.4 mm, the ocular bulb length was 23.33 ± 1.32 and 22.83 ± 1.1 mm, the globe position was 7.66 ± 1.33 and 7.3 ± 1.39 mm, and the width of the optic nerve sheath diameter was 4.65 ± 0.62 and 4.28 ± 0.51 mm, respectively. All measurements were significantly greater for males than for females (p < 0.05). We believe that a practical and quantitative method will be provided by this study for the diagnosis and determination of the normative values of orbital structures.

Normal Diameters of Extraocular Muscles: A Nigerian Retrospective Study.

The thickness of extraocular muscles (EOMs) is important in the management of several conditions associated with EOM enlargement. This study determined the normative values of EOM diameters in adult patients seen at a teaching hospital in Nigeria. The study measured the thickness of the EOMs and the interzygomatic line (IZL) on brain images of 300 patients with non-orbital conditions (150 computed tomography [CT] and 150 magnetic resonance imaging [MRI]) archived in the radiological database of Delta State University Hospital, Nigeria, after ethical clearance. The Statistical Package for the Social Sciences (version 23) was used to obtain descriptive statistics and further compare the variables based on gender, age groups and laterality. The association between parameters was tested using Pearson's correlation test. A probability value of <5% was considered significant. The thickest muscles were the medial rectus (0.42 ± 0.08 cm) and superior muscle group (0.42 ± 0.33 cm) on CT and the inferior rectus (0.40 ± 0.08 cm) on MRI. The diameters were symmetrical with sexual dimorphism in the superior muscle group on CT, medial and lateral recti on MRI and sum of all EOMs on both imaging groups (P < 0.05). The superior muscle group and the sum of all EOMs showed significant age group variations and a positive correlation with age. We noted a positive correlation between each EOM diameter and the sum of all EOMs besides the IZL (P < 0.05). This study offers normative data regarding EOMs that radiologists and ophthalmologists can use to diagnose disease conditions that cause EOM enlargement and further assess their response to treatment.

Effects of various extraocular muscle enlargement patterns on muscle diameter index in graves ophthalmopathy patients: a retrospective cohort study

Graves ophthalmopathy (GO) patients often undergo retrobulbar injection of glucocorticoids (GCs) as a common therapeutic approach. This study aimed to explore the impact of various patterns of extraocular muscle (EOM) enlargement on EOM changes following retrobulbar GCs injection in patients with GO. A retrospective analysis was conducted on GO patients who underwent retrobulbar GCs injections. Data pertaining to EOM diameter (EMD) and muscle diameter index (MDI) were collected from orbital computed tomography (CT) scans. The MDI change (ΔMDI) was calculated by comparing pre- and post-injection MDI values. The relationship between each pre EMD/MDI and ΔMDI was assessed using univariate and multivariate logistic regression analysis. A total of 68 patients with GO were included in this study, accounting for 118 eyes. After retrobulbar injections of GCs, 84 eyes showed a decrease in the MDI, while 34 eyes exhibited an increase in MDI. A threshold effect was observed in the relationship between medial pre EMD/MDI and ΔMDI. When the medial pre EMD/MDI was less than 0.28, a higher medial pre EMD/MDI was associated with a smaller ΔMDI (β = − 25.21, p = 0.0175). However, when the medial pre EMD/MDI was greater than 0.28, no significant association was found between pre EMD/MDI and ΔMDI. There was a negative correlation between medial + lateral pre EMD/MDI and ΔMDI (β = − 11.76, p < 0.0189). A higher medial + lateral pre EMD/MDI was associated with a greater decrease in MDI. Additionally, there was a positive correlation between superior rectus muscle-levator complex (SRLC) pre EMD/MDI and ΔMDI (β = 11.92, p = 0.040). The higher the value of SRLC pre EMD/MDI, the greater the ΔMDI. There was an association between pre EMD/MDI and changes in EOMs after retrobulbar injection of GCs in GO patients. In patients with predominantly enlarged medial rectus muscles and severe degrees of enlargement, retrobulbar injection of GCs should be assessed for its benefit; a combination of medial and lateral rectus muscle enlargement is beneficial for the shrinkage of EOMs following retrobulbar injections; the involvement of the SRLC rectus muscle may be a disadvantageous pattern of shrinkage of EOMs following retrobulbar injections.Trial registration This study is retrospectively registered. We have registered this study with the Chinese Clinical Trials Registry (www.chictr.org.cn, registration number: ChiCTR2200063429).

Extraocular muscle enlargement and proptosis in carotid cavernous fistulas

ABSTRACT Purpose To evaluate the prevalence and pattern of extraocular muscle enlargement and proptosis in patients with carotid cavernous fistulas (CCF). Methods We conducted a retrospective study on patients with digital subtraction angiography (DSA) confirmed CCFs with neuroimaging (computed tomography or magnetic resonance imaging) performed prior to the DSA. The maximum extraocular muscle diameters were recorded. Extraocular muscles were considered enlarged if they were greater than two standard deviations above the normal muscle diameters. Proptosis was defined as the distance between the interzygomatic line to the anterior globe of ≥2 mm compared to the contralateral orbit or ≥21 mm. Results Forty orbits from 20 patients were included. The mean age of participants was 65 ± 15 years and 13 (65%) were female. Thirteen (65%) fistulas were indirect and seven (35%) were direct. There was enlargement of at least one muscle in 11 (27.5%) orbits, and this was not correlated with the type of fistula (direct/indirect). The inferior rectus was most commonly enlarged in seven orbits (17.5%), followed by the medial rectus in five orbits (12.5%). Proptosis was found in 17 (43%) orbits and was more common ipsilateral to the fistula (58% ipsilateral group vs 19% contralateral group, p < .01). Conclusion Extraocular muscle enlargement was observed in over one-fourth of CCFs. When enlarged, the inferior and medial rectus muscles are most commonly involved. These findings may help clinicians and radiologists when evaluating the CT or MRI scans of patients with suspected CCFs.

Risk prediction of dysthyroid optic neuropathy based on CT imaging features combined the bony orbit with the soft tissue structures.

PurposeTo analyze computed tomographic (CT) imaging features of patients with dysthyroid optic neuropathy (DON) retrospectively and deduce a more appropriate predictive model.MethodsThe CT scans and medical records of 60 patients with clinically proven Graves' ophthalmopathy (GO) with (26 women and 10 men) and without DON (16 women and 8 men) were retrospectively reviewed, and 20 age- and sex-matched control participants (12 women and 8 men) were enrolled consecutively. The bony orbit [orbital rim angle (ORA), medial and lateral orbital wall angles (MWA and LWA), orbital apex angle (OAA), and length of the lateral orbital wall (LWL)], and the soft tissue structures [maximum extraocular muscle diameters (Max EOMD), muscle diameter index (MDI), medial and lateral rectus bulk from inter-zygomatic line (MRIZL and LRIZL), proptosis, intraorbital optic nerve stretching length (IONSL), superior ophthalmic vein diameter (SOVD), apical crowding, and presence of intracranial fat prolapse] were assessed on a clinical workstation. The CT features among groups were compared, and a multivariate logistic regression analysis was performed to evaluate the predictive features of DON.ResultsAll bony orbital angle indicators, except ORA (p = 0.461), were statistically different among the three groups (all p < 0.05). The values of MWA, LWA, OAA, and LWL were larger in the orbits with the DON group than in the orbits without the DON group (all p < 0.05). The MDI, MRIZL, proptosis, IONSL, and SOVD were statistically significantly different among the three groups (all p < 0.05), in which the orbits with the DON group were significantly higher than the orbits without the DON group and control group. The apical crowding was more severe in the orbits with the DON group than in the orbits without the DON group (p = 0.000). There were no significant differences in the LRIZL and the presence of intracranial fat prolapse (all p > 0.05). The multivariate regression analysis showed that the MWA, MDI, and SOVD were the independent factors predictive of DON. The sensitivity and specificity for the presence of DON by combining these three indicators were 89 and 83%, respectively.ConclusionBone and soft tissue CT features are useful in the risk prediction of DON, especially the MWA, MDI, and SOVD were the independent factors predictive of DON.

Normative measurements of orbital structures by magnetic resonance imaging

PurposeWe describe and compare the normative values of orbital structures in an Australian cohort on T1-weighted MRI and fat-suppressed contrast-enhanced T1-weighted MRI.MethodsRetrospective review of patients who underwent 3T orbital MRI. The maximum extraocular muscle (EOM) and superior ophthalmic vein (SOV) diameters on normal orbits were recorded. The extraocular muscle diameters were summed to produce the sum of all muscles.ResultsThe normal measurements (mean ± SD) from 141 orbits that had fat-suppressed contrast-enhanced MRI: medial rectus, 4.1 ± 0.5 mm; lateral rectus (LR), 3.9 ± 0.7 mm; superior muscle group (SMG), 4.5 ± 0.7 mm; inferior rectus (IR), 4.6 ± 0.7 mm; and SOV, 1.8 ± 0.7 mm. The normal measurement from 84 orbits that had T1-weighted MRI: MR, 4.1 ± 0.5 mm; LR, 3.4 ± 0.6 mm; SMG, 4.3 ± 0.7 mm; IR, 4.6 ± 0.7 mm; SOV, 2.0 ± 0.7 mm. Eighty-four orbits had both MRI sequences performed. The LR, SMG and the sum of all muscles were significantly larger on fat-suppressed contrast-enhanced T1-weighted MRI sequence than the T1-weighted sequence (P < 0.01), whereas the SOV was significantly larger on the T1-weighted sequence (P < 0.01).ConclusionThese data may aid in diagnosing pathological enlargement of the EOMs and SOV on different scan sequences.

Echographic Assessment of Extraocular Muscle Response to Teprotumumab.

To evaluate extraocular muscle response to teprotumumab using orbital echography in thyroid eye disease. This retrospective study included adult thyroid eye disease patients with pre- and post-teprotumumab orbital echography. Data collected included: age, Hertel measurements, clinical activity score, Gorman diplopia scores, ocular motility, and recti muscle diameters measured by echography. The patient's more proptotic eye before treatment initiation was designated as the study orbit. Ocular motility was assessed by totaling the ductions in all 4 cardinal directions. Orbital echography was obtained pre- and post-treatment to assess response of extraocular muscle diameters. Six patients with a mean age of 67 years were included. There was a mean improvement in proptosis of 4.3 mm in the study eye with 11/12 orbits showing improvement in globe position ( p < 0.05). All patients had a decrease in clinical activity score with a mean reduction of 2.5. Four patients had an improvement in Gorman diplopia score. Ocular motility in the study orbits improved by a total mean of 26.9° ( p < 0.05). Mean total extraocular muscle diameter was reduced from 27.4 to 23.4 mm ( p < 0.001). On average, superior recti were largest pre- and post-treatment, followed by inferior, medial, then lateral recti. However, inferior recti showed the greatest reduction of 23% ( p < 0.02). Orbital echography demonstrated extraocular muscle reduction in all patients after teprotumumab, correlating with improved clinical activity score, ocular motility, and proptosis. Orbital echography is a safe and cost-effective imaging alternative to monitor therapeutic response to teprotumumab.

Orbital structures in the pediatric age group: A normative assessment using magnetic resonance imaging

PurposeMany diseases of traumatic, infectious, endocrinologic and neoplastic origin can lead to orbital involvement and related morphological changes. In the present study, we aimed to determine the age-based normal orbital measurements using magnetic resonance imaging (MRI) in pediatric patients. MethodsOur retrospective study included 186 patients with normal orbital MRI findings. The patients were divided into the following five groups based on their age. Group 1: 1–24 months; Group 2: 25–60 months; Group 3: 61–120 months; Group 4: 121–168 months; and Group 5: 169–216 months. Globe position relative to interzygomatic line (IZL) and orbital rim, optic nerve-sheath complex, extraocular muscle diameters, were measured. ResultsThe differences among the age groups for the distances between cornea and sclera in relation to IZL, for the distances between cornea and sclera relative to orbital rim, and for the extraocular muscle diameters were statistically significant. In terms of the extraocular muscle diameter, it was found that the thinnest muscle of all groups was the lateral rectus muscle while the thickest was the medial rectus muscle. ConclusionIn pediatric patients who were divided into five groups based on their age, the positions of bulbus oculi relative to IZL or orbital rim and the normal diameter ranges of extraocular muscles and of the optic nerve-sheath complex in orbital MRI were determined. We are of the opinion that the presence of such a scale could be a guide in the evaluation of orbital MRI in pediatric patients.

Extraocular muscle diameter in Makurdi, North Central Nigeria: what is normal?

Background: Establishing normal values of extra ocular muscle (EOM) diameter is essential in a given population. Factors including race, region, gender and environment affect the normal diameter of the EOM. The aim of the study was to determine the normal sizes of the EOM in a population in the North Central part of Nigeria using computed tomography (CT).Methods: One hundred and eighty-three CT images of patients who underwent craniofacial imaging for other conditions and who met the inclusion criteria were evaluated. The maximum diameters of the EOMs on coronal reformatted CT images which are the superior group (SG) (superior rectus and the levator palpebral), inferior rectus (IR) medial rectus (MR) and lateral rectus (LR) were assessed.Results: The mean values±SD obtained were 3.65±1.13, 3.93±0.94, 3.40±0.67, 3.43±0.92 for SG, 1R, MR, and LR muscles respectively on the right and 3.61±1.07, 3.86±0.92, 3.34±0.70, 3.42±0.08 for SG, IR MR and LR muscles respectively on the left. The order IR&gt;SR&gt;MR&gt;LR of average muscle diameter was obtained. The females in this region showed slightly higher mean values of the diameter of the EOM than the males; however, this was not statistically significant. By age, there was no consistent correlation.Conclusions: The established normal values of the EOM may serve as a reference point for ophthalmologist and for cosmetic surgeons and also will add to the pool of the existing knowledge for academic purposes.

Normative Measurement of Orbital Structures in Computed Tomography

Introduction: Normal orbital dimensions are important for diagnosing orbital pathologies. Computed tomography (CT) of the orbit is an important modality offering high accuracy for precise measurements of orbit. The study was disbursed to ascertain criteria for the normative values of the various orbital dimensions using computed tomography in patients visiting Tribhuvan University Teaching Hospital, Kathmandu. Methods: Orbital volume, ocular diameter, length of the interzygomatic line (IZL), the distance of the posterior extent of the globe from the interzygomatic line, globe position, diameters of extraocular muscles (medial, lateral, superior group, and inferior rectus) and lens density were measured in each eye of 172 patients undergoing CT examination of paranasal sinuses. The correlations with age and sex were also analyzed. Results: Mean values (mean±SD) of orbital volume, ocular diameter, IZL, globe position and lens density were 24.54±2.57 cm3, 2.44±0.22 cm, 94.3±6.2 mm, 12.3±2.4 mm and 141.43±16.62 HU respectively. Mean diameters of extraocular muscles were 3.67± 0.52 mm, 3.36± 0.50 mm, 3.74±0.42 mm and 3.87±0.38 mm for medial rectus, lateral rectus, inferior rectus and the superior group respectively. There was no significant age and gender difference in most of the measurements. There was significant positive correlation of age with lens density, orbital volume and ocular diameter (p&lt;0.05). Conclusion: Normative data of different orbital measurements were obtained. The present result may help radiologists and ophthalmologists to accurately assess various orbital parameters, particularly in Nepalese populations.

Normative Measurement of Orbital Structures in Computed Tomography

Introduction Normal orbital dimensions are important for diagnosing orbital pathologies. Computed tomography (CT) of the orbit is an important modality offering high accuracy for precise measurements of orbit. The study was disbursed to ascertain criteria for the normative values of the various orbital dimensions using computed tomography in patients visiting Tribhuvan University Teaching Hospital, Kathmandu.&#x0D; MethodsOrbital volume, ocular diameter, length of the interzygomatic line (IZL), the distance of the posterior extent of the globe from the interzygomatic line, globe position, diameters of extraocular muscles (medial, lateral, superior group, and inferior rectus) and lens density were measured in each eye of 172 patients undergoing CT examination of paranasal sinuses. The correlations with age and sex were also analyzed.&#x0D; ResultsMean values (mean±SD) of orbital volume, ocular diameter, IZL, globe position and lens density were 24.54±2.57 cm3, 2.44±0.22 cm, 94.3±6.2 mm, 12.3±2.4 mm and 141.43±16.62 HU respectively. Mean diameters of extraocular muscles were 3.67± 0.52 mm, 3.36± 0.50 mm, 3.74±0.42 mm and 3.87±0.38 mm for medial rectus, lateral rectus, inferior rectus and the superior group respectively. There was no significant age and gender difference in most of the measurements. There was significant positive correlation of age with lens density, orbital volume and ocular diameter (p&lt;0.05).&#x0D; ConclusionNormative data of different orbital measurements were obtained. The present result may help radiologists and ophthalmologists to accurately assess various orbital parameters, particularly in Nepalese populations.

Characterizing Intraorbital Optic Nerve Changes on Diffusion Tensor Imaging in Thyroid Eye Disease Before Dysthyroid Optic Neuropathy.

The aim of this study was to determine whether the optic nerve is affected by thyroid eye disease (TED) before the development of dysthyroid optic neuropathy with diffusion-tensor imaging (DTI). Twenty TED patients and 20 controls were included. The mean, axial, and radial diffusivities and fractional anisotropy (FA) value were measured at the optic nerves in DTI. Extraocular muscle diameters were measured on computed tomography. The diffusivities and FA of the optic nerves were compared between TED and controls and between active and inactive stages of TED. The correlations between these DTI parameters and the clinical features were determined. The mean, axial, and radial diffusivities were lower in TED compared with the controls (P < 0.05). In contrast, FA was higher in TED (P = 0.001). Radial diffusivity was lower in the active stage of TED than the inactive stage (P = 0.035). The FA was higher in the TED group than in the control group (P = 0.021) and was positively correlated with clinical activity score (r = 0.364, P = 0.021), modified NOSPECS score (r = 0.469, P = 0.002), and extraocular muscle thickness (r = 0.325, P = 0.041) in the TED group. Radial diffusivity was negatively correlated with modified NOSPECS score (r = -0.384, P = 0.014), and axial diffusivity was positively correlated with exophthalmos degree (r = 0.363, P = 0.025). The diffusivities and FA reflected changes in the optic nerve before dysthyroid optic neuropathy in TED. The FA, in particular, reflected TED activity and severity.

Study on normal ophthalmic tissues among ocular volume and extraocular muscles structure measurement by HR-MRI

Objective: To measure the ocular volume and extraocular muscles of healthy people using the high-resolution magnetic resonance imaging (HR-MRI) technology, to provide parameters support for eye research, teaching and diagnosis. Methods: The study collected 100 cases of normal subjects (200 eyes) from November 2012 to December 2013, including 50 males and 50 females, accepted line HR-orbital MRI, and image processing software was applied to morphology and statistical analysis. The extraocular muscles, muscle belly level horizontal diameter and maximum diameter vertical diameter were measured. Results: The volume of the vitreous cavity (4.51 ± 0.26) cm 3 had no significant difference with the anatomic normal value ( p = .148); The volumes of the ocular globe, the anterior chamber and the lens cavity were (5.05 ± 0.21) cm 3 , (0.24 ± 0.26) cm 3 , (0.23 ± 0.14) cm 3 , with no statistic differences compared with those of the anatomic normal values. The extraocular muscles of normal Chinese were symmetrical on the two sides. The relationships of the short diameters of extraocular muscles in the maximum planes were: inferior rectus muscle (IR) > medial rectus muscle (MR) > superior rectus (SR) > lateral rectus muscle (LR). Those of the long diameters of extraocular muscles were: LR > MR > SR > IR. Conclusions: MRI can be used for measuring ocular volume and sizes of extraocular muscles. Compared with the anatomic normal value, the sizes of extraocular muscles can also be assessed by the symmetry on the two sides and by observing the usual rule of extraocular muscles.

Refractive changes following corrective surgery for thyroid-related orbitopathy

Thyroid-related orbitopathy (TRO) is a common and recognizable manifestation of Graves' disease, caused by an increase in orbital fat volume, increased extraocular muscle diameter, and fibrosis. Together, within the bony confines of the orbit, these changes might alter the shape and position of the globe, potentially inducing refractive shifts. These refractive changes may then be affected by corrective surgical interventions for TRO such as orbital decompression and strabismus surgery. We studied refractive changes in patients with TRO who underwent strabismus surgery with or without orbital decompression. Manifest refraction was performed preoperatively and postoperatively in 33 patients who met inclusion criteria. Statistically significant postoperative refractive changes were found for cylinder, axis, and spherical equivalent.

Echographic study of extraocular muscle thickness in normal Indian population

PurposeTo establish normative data of extraocular muscle (EOM) dimensions, both vertically and horizontally, using a reproducible echographic method in various age groups. MethodsTwo hundred eyes of 100 healthy subjects (50 males and rest females) were included in this prospective observational study. All subjects were divided into 5 groups with an interval of 10years from 10 to 60years. Each group contained 10 male and 10 female healthy subjects. A single operator took measurements at 4mm distance from the globe plane after drawing a perpendicular line on the globe to the muscle belly. ResultsThe average age of subjects was 37.28±17.14years. Intraobserver reproducibility was very high (intersession concordance correlation co-efficient=0.995). Mean horizontal and vertical diameters of recti were 3.0775 and 8.26mm, respectively. Mean muscle thickness of superior rectus/levator palpebral superioris (LPS) muscle complex and LPS was 4.56 and 1.45mm, respectively. Extraocular muscle diameter increases up to the middle age, then it starts decreasing. There was no statistically significant correlation between diameter of each EOM, both eye and gender (p⩾0.05). There was a non-significant change in extraocular muscle thickness with age. ConclusionThe study provides normative data for extraocular muscle thickness in both genders of various age groups in Indian population. Muscle dimensions do not change significantly with age, between the eyes and gender.

Orbital positron emission tomography/computed tomography (PET/CT) imaging findings in graves ophthalmopathy

BackgroundWe aimed to describe orbital positron emission tomography/computed tomography (PET/CT) imaging findings, both structural and metabolic, in different clinical stages of Graves ophthalmopathy (GO). This prospective, observational, cross-sectional study examined 32 eyes of 16 patients with GO.MethodsPatients were assessed with a complete ophthalmological evaluation and assigned a VISA classification for GO. All patients underwent serum thyroid hormone measurement, antibody profile, and 18-fluorodeoxyglucose positron emission tomography/computed tomography (18-FDG PET/CT) of the orbits. The 18-FDG uptake on PET images was expressed in terms of maximum standard uptake value (SUVmax). CT images were analyzed, and orbital structures were measured in millimeters. Vision, inflammation, strabismus, and overall appearance were assessed according to the VISA classification system, thyroid hormone levels, antibody values, 18-FDG uptake, and thickness of orbital structures.ResultsAltogether, 32 eyes of 16 patients (10 women, 6 men; mean age 44.31 ± 13 years, range 20–71 years) were included. Three patients were hypothyroid, seven were euthyroid, and six were hyperthyroid. CT measurements of extraocular muscle diameter were elevated (P < 0.05), and muscle 18-FDG uptake values were increased. Eyes with a clinical VISA inflammation score of ≤ 4 had an average extraocular muscle SUVmax of 3.09, and those with a score of ≥ 5 had an average SUVmax of 3.92 (P = 0.09), showing no clear correlation between clinically observed inflammation and 18-FDG uptake. 18-FDG uptake values also did not show a correlation with extraocular muscle diameter as measured by CT (R2 = 0.0755, P > 0.05).ConclusionsWe demonstrated a lack of correlation between 18-FDG extraocular muscle uptake and either clinical inflammation score or muscle diameter. Although 18-FDG uptake has been used as an inflammation marker in other pathologies, inflammation in GO may be clinically detected in PET/CT-negative cases, and cases with negative clinical findings may show inflammation on PET/CT. Clinical evaluation is mandatory but may be insufficient and inaccurate for classifying GO. A larger and homogeneous sample size and further research is needed to define the role of PET/CT in detecting, grading, and follow-up of GO to optimize treatment of the inflammatory stage respect clinical methods currently used.

Normative Measurements of Extraocular Musculature by Multislice Computed Tomography

Objective To establish the normal measurements of diameter of extraocular muscles (EOMs) by multislice computed tomography (CT). Methods Orbits of 50 volunteers (25 male and 25 female) were scanned with a multislice CT scanner. For each subject, one axial image at the central level of the eyeball, one coronal image about 1 cm behind globe, and two oblique sagittal images respectively along the left and right optic nerve were used for measurements of the thickness and width of EOMs. The statistic significance of measurement value between male and female and between left and right eyes was evaluated. Results There were no significant differences in the thickness and width of superior muscle group, lateral rectus, medial rectus, lateral rectus, superior oblique, inferior oblique and the thickness of levator palpebrae superioris between the left and right eyes as well as between male and female groups (all P>0.05). The thickness of superior muscle group and inferior rectus had not significant difference (2.9±0.7 vs. 3.3±0.8 mm, P=0.162), while the thickness of medial rectus was significantly higher than that of lateral rectus (3.1±0.5 vs. 2.2±0.6 mm, P=0.000). Conclusions The CT measurement of extraocular musculature is simple and time-saving and can be applied in the clinical work. The normative data obtained may be useful in determining pathologic enlargement of the EOMs in both thyroid-associated orbitopathy patients and other various orbital conditions.

Incomitant Strabismus

The paradigm that an "underacting" extraocular muscle is always atrophic or hypoplastic and that an overacting extraocular muscle should always be enlarged leads to inconsistencies with clinical observations. These include findings of "overacting" inferior oblique muscles, superior rectus muscle overaction or contracture syndrome, and normal extraocular muscle diameters in patients with apparent superior oblique muscle palsy, among other clinical entities. These inconsistencies can be reconciled if one accepts the possibility that extraocular muscle contractile activity may reflect a change in neural input to an anatomically normal muscle or that muscle contractile activity may be altered by shifts in fiber type and distribution within a normal-sized muscle. This remodeling may result from vergence adaptation or from any change in neural stimulus to the muscle. There is substantial evidence to suggest that both of these theoretical possibilities may likely occur.

Incomitant Strabismus: Does Extraocular Muscle form Denote Function?

The paradigm that an underacting extraocular muscle (EOM) is always atrophic or hypoplastic, and an overacting EOM should always be enlarged, leads to inconsistencies with clinical observations. It is inconsistent with the findings of normal extraocular muscle diameters in patients with apparent superior oblique muscle palsy, “overacting” inferior oblique muscles, and the superior rectus muscle overaction/contracture syndrome, among other clinical entities. These inconsistencies can be reconciled if one accepts the possibility that EOM contractile activity may reflect a change in neural input to an anatomically normal muscle, and/or that muscle contractile activity may be altered by a shift in fiber type and distribution within a normal-sized muscle. This remodeling may occur as a result of vergence adaptation or any change in neural stimulus to the muscle. There is substantial evidence to suggest that both these theoretical possibilities may likely occur.

Effect of Near‐Total Thyroidectomy on Thyroid Orbitopathy Due to Toxic Goiter

The relative merit of surgery in the treatment of Graves' ophthalmopathy as well as the extent of surgical resection are still matters of debate. This study aimed at reporting an assessment of the impact of near-total thyroidectomy on the course of ophthalmopathy including exophthalmos. A total of 20 patients with thyrotoxic goiters who were suffering from mild to moderate exophthalmos were enrolled in this prospective study. Preoperative evaluation of ophthalmopathy was accomplished through the NOSPECS classification, magnetic resonance imaging (MRI) for measuring the extraocular muscle diameters, and measurement of the exophthalmos using Hertel's exophthalmometer. Ophthalmopathy including exophthalmos was reevaluated 6 months after operation using the same parameters. Clinical activity evaluation, exophthalmometry, and extraocular muscles measurement by MRI revealed that most of the patients experienced improvement of their ophthalmopathy (65%). This improvement was statistically significant. In addition, no major postoperative complications were observed. However, the study, unlike a number of reported retrospective ones, failed to specify any statistically significant prognostic factors affecting the course of ophthalmopathy; this may have been due to the limited number of patients. In addition, all of the patients were of relatively young age and thyrotoxic, and most were female and nonsmoking. In addition to the fact that near-total thyroidectomy adds the advantages of total thyroidectomy (no recurrence) to those of subtotal thyroidectomy (low incidence of temporary and permanent hypoparathyroidism), it has a significant positive impact on thyroid-associated orbitopathy.