Whole-orbit-based multiparametric assessment of disease activity of thyroid eye disease on Dixon MRI.

PURPOSE: This study aimed to explore the diagnostic value of whole-orbit-based multiparametric assessment on Dixon MRI for the evaluation of the thyroid eye disease (TED) activity. METHODS: The retrospective study enrolled patients diagnosed as TED and obtained their axial and coronal Dixon MRI scans. Multiparameters were assessed, including water fraction (WF), fat fraction (FF) of extraocular muscles (EOMs), orbital fat (OF), and lacrimal gland (LG). The thickness of OF and herniation of LG were also measured. Univariable and multivariable logistic regression was applied to construct prediction models based on single or multiple structures. Receiver operating characteristic (ROC) curve analysis was also implemented. RESULTS: Univariable logistic analysis revealed significant differences in water fraction (WF) of the superior rectus (P = 0.018), fat fraction (FF) of the medial rectus (P = 0.029), WF of OF (P = 0.004), and herniation of LG (P = 0.012) between the active and inactive TED phases. Multivariable logistic analysis and corresponding receiver operating characteristic curve (ROC) analysis of each structure attained the area under the curve (AUC) values of 0.774, 0.771, and 0.729 for EOMs, OF, and LG, respectively, while the combination of the four imaging parameters generated a final AUC of 0.909. CONCLUSIONS: Dixon MRI may be used for fine multiparametric assessment of multiple orbital structures. The whole-orbit-based model improves the diagnostic performance of TED activity evaluation.

Quantitative T1 mapping MRI for the assessment of extraocular muscle fibrosis in thyroid-associated ophthalmopathy.

PURPOSE: We aimed to investigate the performance of T1 mapping and its histological correlation with extraocular muscle fibrosis in thyroid-associated ophthalmopathy (TAO). METHODS: We prospectively recruited 12 cases of active TAO, 12 cases of inactive TAO, and 15 cases of control subjects. All participants underwent magnetic resonance imaging (MRI) scan with pre-/postcontrast T1 mapping and short-time inversion-recovery (STIR) sequence. The images were analyzed to obtain precontrast T1, extracellular-volume (ECV) fraction on T1 mapping, and signal-intensity ratio (SIR) on STIR for each rectus. Muscle biopsy was performed at lateral rectus to quantify-collagen volume fraction, glycosaminoglycan (GAG)-volume fraction, and extracellular space component. The relationship between MRI and histopathology was examined with Pearson correlation coefficient. RESULTS: The active TAO group was characterized with GAG accumulation, while the inactive TAO group presented with substantial fibrosis. The MRI parameters achieved acceptable interobserver and intraobserver agreement. The precontrast T1 and ECV remarkably increased in the TAO groups than the control group, and ECV positively correlated with collagen-volume fraction (r = 0.913) and extracellular-space component (r = 0.886) in the inactive TAO group. The SIR statistically increased in the active TAO group, and SIR positively correlated with GAG-volume fraction in all three groups. The performance of ECV (cutoff > 48.1%) to screen out extraocular muscle fibrosis in inactive TAO was 60.9% sensitivity and 93.3% specificity. CONCLUSIONS: The ECV parameter on T1 mapping MRI is a reliable tool to quantify extraocular muscle fibrosis, providing insights into noninvasive evaluation of pathological changes in TAO orbit. TRIAL REGISTRATION NUMBER: ChiCTR2000040394; Date of registration: 28 November 2020.

MR-Eye: High-Resolution Microscopy Coil MRI for the Assessment of the Orbit and Periorbital Structures, Part 2: Clinical Applications.

In the first part of this 2-part series, we described how to implement microscopy coil MR imaging of the orbits. Beyond being a useful anatomic educational tool, microscopy coil MR imaging has valuable applications in clinical practice. By depicting deep tissue tumor extension, which cannot be evaluated clinically, ophthalmic surgeons can minimize the surgical field, preserve normal anatomy when possible, and maximize the accuracy of resection margins. Here we demonstrate common and uncommon pathologies that may be encountered in orbital microscopy coil MR imaging practice and discuss the imaging appearance, the underlying pathologic processes, and the clinical relevance of the microscopy coil MR imaging findings.

Prolapse of Orbital Fat through the Inferior Orbital Fissure: Description, Prevalence, and Assessment of Possible Pathologic Associations.

BACKGROUND AND PURPOSE: A few patterns of orbital fat prolapse have been described. Some are associated with disease, and others may mimic a neoplasm. We have observed prolapse of orbital fat into the infratemporal fossa via the inferior orbital fissure on MR imaging. The clinical relevance of this finding, if any, is unknown. The purposes of this study were to describe the MR imaging appearance of orbital fat prolapse through the inferior orbital fissure, to estimate the prevalence of this finding, and to assess possible pathologic associations. MATERIALS AND METHODS: For this retrospective study of 228 orbital MR imaging examinations, 3 neuroradiologists independently assessed the presence of prolapse on high-resolution T1-weighted images. Discrepancies were resolved by consensus, and interobserver agreement was calculated. Patient demographics, indications for imaging, and pertinent clinical history were recorded. One-way analysis of variance and the Fisher exact test were used to assess possible associations between prolapse and specific patient characteristics. RESULTS: Orbital fat prolapse through the inferior orbital fissure was observed in 20/228 patients (9%). This finding was unilateral in 11 patients (55%) and bilateral in 9 patients (45%). There was no significant association with age, sex, obesity, Graves disease, hypercortisolism, prior orbital trauma, proptosis, or enophthalmos. Interobserver agreement was 90%. CONCLUSIONS: Prolapse of orbital fat into the infratemporal fossa via the inferior orbital fissure is a relatively common finding on orbital MR imaging that has no identified pathologic association. Neuroradiologists should recognize this finding so as not to report it as pathologic.

Assessment of Orbital Computed Tomography (CT) Imaging Biomarkers in Patients with Thyroid Eye Disease.

To understand potential orbital biomarkers generated from computed tomography (CT) imaging in patients with thyroid eye disease. This is a retrospective cohort study. From a database of an ongoing thyroid eye disease research study at our institution, we identified 85 subjects who had both clinical examination and laboratory records supporting the diagnosis of thyroid eye disease and concurrent imaging prior to any medical or surgical intervention. Patients were excluded if imaging quality or type was not amenable to segmentation. The images of 170 orbits were analyzed with the developed automated segmentation tool. The main outcome measure was to cross 25 CT structural metrics for each eye with nine clinical markers using a Kendall rank correlation test to identify significant relationships. The Kendall rank correlation test between automatically calculated CT metrics and clinical data demonstrated numerous correlations. Extraocular rectus muscle metrics, such as the average diameter of the superior, medial, and lateral rectus muscles, showed a strong correlation (p < 0.05) with loss of visual acuity and presence of ocular motility defects. Hertel measurements demonstrated a strong correlation (p < 0.05) with volumetric measurements of the optic nerve and other orbital metrics such as the crowding index and proptosis. Optic neuropathy was strongly correlated (p < 0.05) with an increase in the maximum diameter of the superior muscle. This novel method of automated imaging metrics may provide objective, rapid clinical information. This data may be useful for appreciation of severity of thyroid eye disease and recognition of risk factors of visual impairment from dysthyroid optic neuropathy from CT imaging.

Comparative assessment of Graves' disease and main extrathyroidal manifestation, Graves' ophthalmopathy, by non-targeted metabolite profiling of blood and orbital tissue.

Graves' disease (GD) is an autoimmune disorder that causes the overproduction of thyroid hormones and consequent cascade of systemic metabolism dysfunction. Moreover, Graves' ophthalmopathy (GO) is the main extrathyroidal manifestation of Graves' disease (GD). The goal of the study was to identify metabolic signatures in association with diagnostic biomarkers of GD without GO and GO, respectively. Ninety metabolites were profiled and analyzed based on a non-targeted primary metabolite profiling from plasma samples of 21 GD patients without GO, 26 subjects with GO, and 32 healthy subjects. Multivariate statistics showed a clear discrimination between healthy controls and disease group (R2Y = 0.518, Q2 = 0.478) and suggested a biomarker panel consisting of 10 metabolites. Among them, most of metabolites showed the positive association with the levels of thyrotropin receptor antibodies. With combination of proline and 1,5-anhydroglucitol, which were identified as GO-specific modulators, the re-constructed biomarker model greatly improved the statistical power and also facilitated simultaneous discrimination among healthy control, GO, and GD without GO groups (AUC = 0.845-0.935). Finally, the comparative analysis of tissue metabolite profiles from GO patients proposed putative metabolic linkage between orbital adipose/connective tissues and the biofluidic consequences, in which fumarate, proline, phenylalanine, and glycerol were coordinately altered with the blood metabolites.

Quantitative assessment of orbital fractures in Asian patients: CT measurement of orbital volume.

Enophthalmos is caused by an increase of orbital volume after blowout fracture and is one of the most critical complications of such fractures, but is often masked by swelling soon after injury. If surgery is performed after swelling resolves, it becomes more difficult to treat enophthalmos because of atrophy and fibrosis. Accordingly, it is important to estimate the severity of enophthalmos soon after injury. We developed a new criterion for determining whether orbital fractures are indicated for surgery in Asian patients using analysis of orbital volume. We retrospectively calculated the orbital volume of patients treated surgically or conservatively and analyzed the correlation between changes of orbital volume and the severity of enophthalmos. Regression analysis of the correlation between enophthalmos and increased orbital volume (y = 0.8x + 0.2; correlation coefficient: 0.92) showed that enophthalmos of 2.0 mm corresponded to an increase in orbital volume of 2.25 cm3. This result is similar to data reported previously for Caucasian patients - enophthalmos of 2.0 mm is a common surgical indication worldwide. Our results suggest that an increase of orbital volume of >2.25 cm3 could be a new criterion for surgical treatment of blowout fractures in Asians.

Serum IgG2 and tissue IgG2 plasma cell elevation in orbital IgG4-related disease (IgG4-RD): Potential use in IgG4-RD assessment.

AIMS: To determine the role of serum and tissue IgG2 in orbital biopsies with the histological features of IgG4-related disease (IgG4-RD) in comparison with non-IgG4-related orbital inflammatory disorders (OID), including autoimmune disorders. METHODS: This is an international (Sheffield, UK, and Singapore) collaborative, retrospective case review of 69 patients (38 from Singapore National Eye Centre and 31 from Royal Hallamshire Hospital, Sheffield) with orbital inflammatory biopsies between 2002 and 2016. Clinical information and histology were reviewed and cases were classified into three groups: Group 1: IgG4-RD orbital inflammation (n=43); Group 2: idiopathic OID (n=12) and Group 3: autoimmune OID (n=14). Serum IgG1, IgG2, IgG3 and IgG4 levels were collated where available and immunohistochemistry (IHC) for tissue IgG2 plasma cells was performed. RESULTS: Dual IHC showed IgG2 plasma cells as a distinct population from IgG4 plasma cells. Significant (twofold) serum IgG2 elevation was noted among IgG4-RD (group 1), idiopathic (group 2) and autoimmune OID (group 3). Similarly, significant elevation of tissue IgG2 plasma cells was also seen among IgG4-RD (group 1), idiopathic and autoimmune OID (groups 2 and 3). CONCLUSIONS: Significant elevations of serum IgG2 and tissue IgG2 plasma cells are present in orbital IgG4-RD in comparison with non-IgG4 orbital inflammation (idiopathic and autoimmune OID), suggesting that IgG2 may play a role in IgG4-RD. A serum IgG2 cut-off >5.3 g/L was found to be 80% sensitive and 91.7% specific for orbital IgG4-RD, with an accuracy of 0.90. Tissue IgG2 and IgG4 subclass reporting may provide additional insight regarding the 'IgG4-RD' pathogenesis.

Use of 3D orbital reconstruction in the assessment of orbital sexual dimorphism and its pathological consequences.

INTRODUCTION: Surrounded by a variety of structures including the facial sinuses and the brain, the human orbit displays unique anatomical features. It is known that orbital volume correlates with age and sex. The aim of this study was to evaluate sexual dimorphism of orbital volume relative to the size of the skull, and to establish criteria for gender determination. METHODS: Orbital volume was measured from 3D models of the orbits. The volumes were expressed in relation to the centroid size of the skull, to ensure that any sexual dimorphism in orbital volume was not simply due to a difference in skull size. Thirty-three male and 42 female subjects were included in the study. RESULTS: The volume of both orbits were significantly higher in men than in women (P=0.0001). The right, left and total orbital volumes relative to the centroid skull size were also significantly higher in men than women (P<0.05). The method was repeatable and reproducible. A test of gender determination was developed, with a precision of 77.3%. DISCUSSION: This is the first study showing a sexual dimorphism in orbital volume relative to skull size. This difference in volume could explain the greater predisposition to myopia in women and their more frequent need for orbital decompression in thyroid orbitopathies.

Cephalometric assessment of soft tissue morphology of patients with acromegaly.

AIM: To assess the sagittal soft tissue morphology of patients with acromegaly in comparison with a healthy control group. METHODS: Twenty-seven patients with acromegaly (11 male, 16 female; mean age 47.3 ± 11.5 years) and 30 healthy subjects (15 male, 15 female; mean age 42.2 ± 17.4 years) were included in the study. Linear and angular measurements were made on lateral cephalograms to evaluate soft tissue and skeletal characteristics. The intergroup comparisons were analysed with the Student's t-test. RESULTS: Facial convexity (p < 0.01) and the nasolabial angle (p < 0.001) were reduced in patients with acromegaly, whereas nose prominence (p < 0.01), upper lip sulcus depth (p < 0.01), upper lip thickness (p < 0.01), basic upper lip thickness (p < 0.01), lower lip protrusion (p < 0.05), mentolabial sulcus depth (p < 0.05) and soft tissue chin thickness (p < 0.001) were increased. Anterior cranial base length (p < 0.05), the supraorbital ridge (p < 0.01), the length of the maxilla and mandible (p < 0.001, p < 0.01, respectively) were significantly increased, and mandibular prognathism was an acromegalic feature (p < 0.05). CONCLUSION: Acromegalic coarsening and thickening of the craniofacial soft tissues was identified from lateral cephalograms, which may therefore contribute to early diagnosis when evaluated together with other changes caused by the disease.

Diagnostic value of high-resolution peripheral quantitative computed tomography (HR-pQCT) in the qualitative assessment of cribra orbitalia: a preliminary study.

Cribra orbitalia are a porotic or sieve-like lesions in the bony orbital roof. This characteristic has frequently been detected in palaeopathological skulls from many parts of the world and has been the object of extensive research. Our objective was to determine if high-resolution peripheral quantitative computed tomography (HR-pQCT) could produce reliable information in the study of cribra orbitalia. Seven skulls displaying cribra orbitalia were investigated by HR-pQCT. The two-dimensional slices were compared with histological sections. The HR-pQCT images and histological sections showed similar results, i.e. two groups of lesions with different characteristics. HR-pQCT can be of great value in palaeopathological research. It is a nondestructive, fast and precise technique that allows an easy evaluation of the bone architecture without destruction of the sample.

Comparison between rapid and mixed maxillary expansion through an assessment of dento-skeletal effects on posteroanterior cephalometry.

BACKGROUND: The aim of this study is to compare the dento-skeletal effects of rapid maxillary expansion (RME) and mixed maxillary expansion (MME), assessed on posteroanterior (PA) cephalograms. METHODS: Treatment groups consisted of 42 patients; mean age in RME group (n = 21,13 female and 8 male subjects) was 8.8 years ± 1.37 at T0 and 9.6 years ± 1.45 at T1 and mean age in MME group (n = 21, 12 female and 9 male patients) was 8.9 years ± 2.34 at T0 and 10.5 years ± 2.08 at T1. Seventeen bilateral anatomic landmarks, 16 linear (12 skeletal and 4 dental) and 4 angular measurements were assessed for each patient at T0 and T1. Data from the two groups were compared using independent sample t test (p < 0.05). RESULTS: At T0, the groups were similar for all examined variables (p > 0.05). Significant and equal increase of lateronasal and maxillary and upper and lower molar widths (p < 0. 01) occurred in both groups at T1. Significant but different increases were observed for maxillary incisal, upper left first molar-lateroorbitale, and maxillary first molar angles (p < 0.001 vs. p < 0.05). Significant increases were reported for upper inter-incisal width apex (p < 0.001) and upper right first molar-lateroorbitale angle (p < 0.05) only in the RME group. At T1, differences in maxillary incisal angle (p < 0.05), upper left first molar-lateroorbitale, and maxillary first molar angles (p < 0.001) were noted. CONCLUSIONS: RME and MME were both effective to increase skeletal transverse dimensions by opening mid-palatal suture in growing patients, while MME was associated with minor dental side effects than RME.

Robust and regional 3D facial asymmetry assessment in hemimandibular hyperplasia and hemimandibular elongation anomalies.

Hemimandibular hyperplasia (HH) and hemimandibular elongation (HE) anomalies present with facial asymmetry and deranged occlusion. Currently, diagnosis and assessment of the facial dysmorphology is based on subjective clinical evaluation, supported by radiological scans. Advancements in objective assessments of facial asymmetry from three-dimensional (3D) facial scans facilitate a re-evaluation of the patterns of facial dysmorphology. Automated, robust and localised asymmetry assessments were obtained by comparing a 3D facial scan with its reflected image using a weighted least-squares superimposition. This robust superimposition is insensitive to severe asymmetries. This provides an estimation of the anatomical midline and a spatially dense vector map visualising localised directional differences between the left and right hemifaces. Analysis was conducted on three condylar hyperplasia phenotypes confirmed by clinical and CT evaluation: HH; HE; and hybrid phenotype. The midline extraction revealed chin point displacements in all cases. The upper lip philtrum and nose tip deviation to the affected side and a marked asymmetry of the mid face was noted in cases involving HE. Downward and medial rotation of the mandible with minor involvement of the midface was seen in the HH associated deformity. The hybrid phenotype case exhibited asymmetry features of both HH and HE cases.

Assessment of the posteroanterior cephalograms of the parents of children with cleft lip and/or cleft palate in Latvia.

OBJECTIVE: To compare the craniofacial morphology of parents of children with cleft lip with or without palate (CL±P), children with isolate cleft palate (CP) and individuals without family history of orofacial clefting in Latvia. MATERIALS AND METHODS: Posteroanterior (PA) cephalograms were obtained from all participants: 37 couples of noncleft biological parents of children with nonsyndromic CL±P and 17 couples of noncleft biological parents of children with nonsyndromic CP (the parents groups were made dividing the parents after gender and children cleft type). The control groups consisted of 40 females and 42 males, who had no history of clefts in the family. A conventional cephalometric analysis was used to measure various measurements of facial widths. RESULTS: Statistically significant differences (decreased facial and biorbital width) were found between fathers of children with CP and males from the control group. Results showed asymmetry of zygomatic width (left side dominance) in all parents groups compared with the control groups. The asymmetry was detected in maxillary part (left side dominance) in CP children mothers and females and males control groups. CONCLUSION: Some statistical significant differences in the PA cephalometric measurements among parents groups of children with CL±P and CP, and control groups were found. However the differences among study groups and the control groups were small, often not larger than variations in the population.

3D assessment of morbidity associated with lower eyelid incisions in orbital trauma.

This study compared the morbidity associated with transconjunctival and transcutaneous approaches for orbital floor exploration with respect to the position of the lower eyelid following surgery. Two groups of 32 volunteers and 32 patients (12 transconjunctival and 20 transcutaneous) were recruited and three-dimensional (3D) imaging was carried out at 6 months following surgery. In the transcutaneous group, there were significant variations in the shape of the lower eyelid, with more medial displacement of the exocanthion. No significant differences were detected in the transconjunctival group compared to controls. The use of a 3D imaging system provided an objective method of assessing this aspect of morbidity associated with the use of lower eyelid incisions.

Assessment of the volume of intraorbital structures using the numerical segmentation image technique (NSI): the extraocular muscles.

INTRODUCTION: In recent years the use of computer systems has allowed numerical analysis of medical images to be introduced and has speeded up the conversion of numerical data into clinically valuable information. The creation of a software application that could almost automatically calculate the volume of anatomical structures imaged by MRI has seemed possible. The aim of our study was to determine the clinical usefulness of an numerical segmentation image technique (NSI) software application in estimating the volume of extraocular muscles. MATERIAL AND METHODS: The study group was formed of 45 patients (90 orbits). All the patients underwent MRI examinations of the orbits by a 1.5 T scanner using a head coil. The degree of exophthalmos was determined clinically and radiologically in relation to the interzygomatic line. The quantitative assessment of all eye muscles was carried out using the NSI application, a new software program introduced by the authors. RESULTS: A close correlation between muscle volume and the degree of exophthalmos was revealed and confirmed by statistical analysis (r = 0.543, p = 3.13396E-08) in agreement with other papers. CONCLUSIONS: The NSI software program is an application which offers a reliable and precise estimation of eye muscle volume. It is therefore useful in the diagnosis of the pathological processes leading to exophthalmos. It has special clinical value for monitoring discrete volume changes of muscles during treatment.

Assessment of inflammation in idiopathic orbital myositis with fat-suppressed T2-weighted magnetic resonance imaging.

PURPOSE: To evaluate the inflammation in idiopathic orbital myositis by fat-suppressed T2-weighted magnetic resonance imaging (MRI). DESIGN: Observational case series. METHODS: The inflammation in nine patients with orbital myositis was evaluated with fat-suppressed T2-weighted MRI within three weeks of onset. Patients were mainly treated with steroid pulse therapy and followed to the acute improvement or chronic ocular motility restriction phases. RESULTS: Each patient was found to have localized inflammations in the extraocular muscles or associated fascial structures. Of the five patients with acute improvement, none had inflammation of the extraocular muscles, whereas the four patients with chronic ocular motility restriction had inflammation of the extraocular muscles. CONCLUSION: These results suggest that acute or chronic pattern in orbital myositis is correlated with the localized inflammation. The inflammation in the extraocular muscles may be one of the factors that lead to the chronic ocular motility restriction.

[Cribra orbitalia, dentin hypoplasia and life expectancy of 20-year-old persons as social and sex specific stress indicators in correlation with the health status of an early medieval population]. / Cribra orbitalia, Schmelzhypoplasie und Lebenserwartung der 20 jährigen als sozial- und geschlechtsspezifische Stressindikatoren bezüglich der Gesundheitssituation einer frühmittelalterlichen Bevölkerung.

The aim of this study is based on the analysis of diachronically social and sexual specific considerations on the life situation of the early medieval population of Schleitheim, Kanton Schaffhausen, Switzerland. Cribra orbitalia and the linear enamel hypoplasia of the teeth are considered as stressors. This study is based on the life expectancy of the 20 years old, as the life expectancy gives information on the health condition of a social group or an entire population. The considered indicators show the same tendencies in three of the four social groups (women social group A and group B/C, men of the social group A). The female and male population of the social group A show a steady decrease in the indicator from the 5th century to come to its lowest level in the 7th century. The same parameters indicate a continuous increase in stress for the female population of the group B/C. Only one of the three indicators, the Cribra orbitalia, shows a positive tendency in the male population of the social group B/C from the 6th century to the following period, while hypoplasia and the life expectancy on the other hand indicate a negative tendency. The results show equal tendencies in the three independent indicators concerning three of the four social groups. This proves the high reliability of the indicators. These results are astonishing in two ways. First of all, the tendencies show that the originally better life situation of women of the higher ranking social group decreases in the following periods, whereas the women of the lower social group show an inverse development. This female population of low life situation in the 5th century shows an increase in life qualities in the following periods. Remarkable, too, is the fact, that the female population of both social groups shows a lower level of stress than the corresponding male population. This fact is astonishing, as we would expect inverse results in a patriarchal society. This may point to a well known fact: Women show a higher vitality than the male population.

20 MHz high frequency ultrasound assessment of scleral and intraocular conjunctival squamous cell carcinoma.

AIM: To assess in a prospective manner, high frequency ultrasound diagnosis of deep invasion by conjunctival squamous cell carcinoma. METHODS: Prospective, non-randomised case series comparing 20 MHz high frequency ultrasonographic and clinicopathological data. RESULTS: 20 MHz high frequency ultrasound delineated the degree of deep involvement of this tumour into the sclera, globe, and orbit. The results of ultrasonography correlated with the clinicopathological results. CONCLUSIONS: High frequency ultrasound is a useful diagnostic adjunctive test in patients with possible deep involvement by a conjunctival squamous cell carcinoma.

Assessment of optic nerve compression in Graves' ophthalmopathy. The usefulness of a quick T1-weighted sequence.

PURPOSE: Diagnosis of optic nerve compression can be difficult in patients with equivocal clinical signs. We examined the usefulness of a quick coronal MR sequence performed at a predetermined plane as a screening tool for selecting patients at high risk of optic nerve compression. MATERIAL AND METHODS: Direct coronal images of the orbit were obtained in 37 patients with Graves' disease in a predetermined plane. The muscular indices (MI) of each orbit were calculated. Mann-Whitney U-Wilcoxon rank sum test was used to assess if there was any statistically significant difference between patients with and without signs of optic nerve compression. The ROC curve was used to identify a value useful for discriminating patients with a higher risk of developing optic nerve compression. RESULTS: There was a statistically significant difference (p<0.05) in the MI between patients with and without optic nerve compression. An MI of -0.48 had 100% sensitivity, 89% specificity and 91% accuracy in identifying patients with optic nerve compression. CONCLUSION. A quick coronal MR image obtained at the mid-orbital plane is useful in screening patients with Graves' disease for optic nerve compression.