Radiologic measurement of extraocular muscle volumes in patients with Graves' orbitopathy: a review and guideline

Impact of sphenoid trigone size and extraocular muscle thickness on the outcome of lateral wall orbital decompression for thyroid eye disease

BACKGROUND

To retrospectively review lateral wall orbital decompression for thyroid eye disease (TED) and to evaluate pre-operative CT scans to analyse the variation in proptosis reduction.

METHODS

Consecutive lateral wall orbital decompressions performed by a single surgeon were retrospectively reviewed. Pre-operative CT scan features and post-operative proptosis reduction were analysed. The sphenoid trigone cross-sectional areas were summed and multiplied by the slice thickness to yield bone volume. Cumulative extraocular muscle thickness was calculated by combining the maximum thickness of the four recti. "Trigone volume" and "cumulative muscle thickness" were correlated with proptosis reduction at 3 months post-surgery.

RESULTS

Out of 73 consecutive lateral wall orbital decompressions, 17 orbits had prior endonasal medial wall orbital decompression. In the remaining 56 orbits, the mean pre-operative and post-operative proptosis were 24.3 ± 1.6 mm and 20.9 ± 2.3 mm respectively. The proptosis reduction ranged from 1 to 7 mm (mean of 3.5 mm ± 1.3 (p < 0.001)). Mean sphenoid trigone volume was 895 ± 434.4 mm3. The mean cumulative muscle thickness was 20.4 ± 5 mm. The correlation coefficient between muscle thickness and proptosis reduction was - 0.3 and was statistically significant (p = 0.043). The correlation coefficient between sphenoidal trigone volume and proptosis reduction was 0.2 (p = 0.068). With a multivariate analysis, the coefficient of efficient of regression for muscle thickness was - 0.007 (p = 0.42) and the coefficient of regression for trigone volume was 0.0 (p = 0.046).

CONCLUSION

Proptosis reduction following lateral wall orbital decompression can be variable. Extraocular muscle thickness had a significant correlation with the outcome, with greater proptosis reduction in orbits with thin muscles. The sphenoidal trigone size had a weak correlation with decompression outcome.

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).

A clinical study of the effect of 3D reconstruction on exophthalmos after an operation on an old orbital wall fracture

BACKGROUND

Orbital blowout fracture is common in ocular trauma. Accurate measurement of orbital volume after fracture is key in improving intraocular correction.

OBJECTIVE

This study aims to explore the impact of 3D reconstruction technology in restoring normal exophthalmos in patients with old orbital wall fractures.

METHODS

A total of 31 patients were randomly divided into an experimental group (n= 15) and a control group (n= 16). For orbital wall repair and reconstruction, the conventional group used the conventional surgical scheme, and the 3D group used 3D printing technology.

RESULTS

There was no statistical difference between the preoperative mean extraocular muscle volume of the healthy eye and the affected eye. However, the mean orbital volume (24.76 vs 27.11, P= 0.005) and mean retrobulbar fat volume (17.53 vs 16.42, P= 0.006) were significantly different between the healthy eye and the affected eye. After an average follow-up of 16 weeks, the differences in pre- and post-surgery exophthalmos in the two groups were 0.42 ± 0.08 mm and 1.63 ± 0.51 mm, respectively. The difference between the two groups was statistically significant (t= 4.42, P= 0.003). The complications were not statistically different.

CONCLUSION

Using 3D reconstruction technology preoperatively can significantly improve exophthalmos in patients with old orbital wall fractures.

Prospective Evaluation of Intraorbital Soft Tissue Atrophy after Posttraumatic Bone Reconstruction: A Risk Factor for Enophthalmos

Orbital fractures are a common finding in facial trauma, and serious complications may arise when orbital reconstruction is not performed properly. The virtual planning can be used to print stereolithographic models or to manufacture patient-specific titanium orbital implants (PSIs) through the process of selective laser melting. This method is currently considered the most accurate technique for orbital reconstruction. Even with the most accurate techniques of bone reconstruction, there are still situations where enophthalmos is present postoperatively, and it may be produced by intraorbital soft tissue atrophy. The aim of this paper was to evaluate the orbital soft tissue after posttraumatic reconstruction of the orbital walls’ fractures. Ten patients diagnosed and treated for unilateral orbital fractures were included in this prospective study. A postoperative CT scan of the head region with thin slices (0.6 mm) and soft and bone tissue windows was performed after at least 6 months. After data processing, the STL files were exported, and the bony volume, intraorbital fat tissue volume, and the muscular tissue volume were measured. The volumes of the reconstructed orbit tissues were compared with the volumes of the healthy orbit tissues for each patient. Our findings conclude that a higher or a lower grade of fat and muscular tissue loss is present in all cases of reconstructed orbital fractures. This can stand as a guide for primary or secondary soft tissue augmentation in orbital reconstruction.

Increased Orbital Muscle Fraction Diagnosed by Semi-Automatic Volumetry: A Risk Factor for Severe Visual Impairment with Excellent Response to Surgical Decompression in Graves’ Orbitopathy

Graves’ orbitopathy (GO) leads to increased orbital tissue and causes symptoms such as exophthalmos, functional complaints, or dysthyroid optic neuropathy. Different GO types with fat and/or muscle enlargement were identified, and increased muscle appears to particularly influence visual status and treatment response. The current study examines visual parameters dependent on orbital muscle volume fraction in a surgically treated GO cohort. After volumetric analysis of the preoperative orbital content, 83 orbits in 47 patients were categorized into predefined groups (increased or not-increased muscle fraction). All cases underwent pterional orbital decompression, and pre- and postoperative visual status was retrospectively analyzed. Forty-one orbits revealed increased and 42 orbits revealed not-increased muscle volume (mean fraction 29.63% versus (vs.) 15.60%). The preoperative visual acuity (VA) was significantly lower in orbits with increased vs. not-increased muscle volume (mean VA 0.30 vs. 0.53, difference 2.5 lines). After surgery, mean VA improved significantly by 1.7 lines in orbits with increased muscle volume. Not preoperative, but postoperative exophthalmos was significantly lower in orbits with not-increased muscle volume. Increased orbital muscle is associated with significantly reduced VA, but can be remarkably improved by pterional orbital decompression. Therefore, surgical therapy should be considered particularly in decreased VA with orbital muscle enlargement.

Risk Factors for New Onset Diplopia After Graduated Orbital Decompression

PURPOSE

The aim of the study was to identify possible risk factors for new onset diplopia in 20° of primary position (NOD PP) after orbital decompression. A predisposition for NOD has been established for patients with pre-existing diplopia in secondary gaze; therefore, the authors focused on patients without preoperative diplopia.

METHODS

Retrospective chart review of patients who underwent balanced orbital decompression between 2012 and 2019 due to Graves orbitopathy at the authors' institution. Exclusion criteria were incomplete clinical data set, revision surgery, and medial or lateral decompression only. The following clinical parameters were evaluated preoperatively and postoperatively: Hertel exophthalmometry, objective measurement of misalignment using the prism-cover-test, assessment of the field of binocular single vision, and measurement of monocular excursions. In addition, the diameter of the extraocular eye muscles was measured in all preoperative CT scans.

RESULTS

We included 327 patients (612 orbits), 126 patients (242 orbits) had no preoperative diplopia. In patients with NOD PP (34%, n = 43/126), enlargement of the medial rectus muscle and restriction of abduction and elevation were significantly more frequent than in patients with no NOD PP. The degree of exophthalmos decrease positively correlated with postoperative squint angle.

CONCLUSION

We were able to identify the diameter of the medial rectus muscle, restriction of abduction, and elevation as well as an extensive reduction of exophthalmos as risk factors for NOD PP in patients with no preoperative diplopia.

Age-related difference in extraocular muscles and its relation to clinical manifestations in an ethnically homogenous group of patients with Graves' orbitopathy

PURPOSE

To evaluate the age-related difference in EOMs and its relation to clinical manifestations by computed tomography (CT) measurement of EOMs.

METHODS

The medical records and CT image review of 40 patients (80 orbits) with moderate-to-severe Graves' orbitopathy were performed. The patients were divided into two age groups, group 1 (≤ 40 years) and group 2 (> 40 years). CT scans of 30 gender- and age-matched normal controls were also obtained. The maximal cross-sectional area (MCA) and its position (pMCA) of each EOM were measured.

RESULTS

Group 1 presented with more severe proptosis (p < 0.001), while group 2 had a higher risk of diplopia (p < 0.001). Motility restriction in supraduction was more likely to occur in Group 2 (p = 0.027) with even higher severity (p = 0.047). The pMCA was higher in the inferior (p = 0.001), medial (p = 0.021), and lateral rectus (p = 0.013) in group 1. Proptosis was positively correlated to pMCA while diplopia was correlated to MCA in both groups. Significant correlation was noted between restrictions levels and MCA (superior, r = 0.467, p < 0.001; inferior, r = 0.358, p = 0.007; medial, r = 0.314, p = 0.018; lateral, r = 0.308, p = 0.021) or pMCA (inferior, r =  - 0.534, p < 0.001) only in group 2.

CONCLUSIONS

The muscle enlargement patterns are significantly different between younger and older patients. Older patients tended to have enlarged muscle bellies more posterior in the orbit, which is responsible for more diplopia and motility restriction. Proptosis is more likely to be affected by the most enlarged position than muscle size. So younger patients tended to develop more proptosis and be less bothered by motility restriction even with enlarged muscles.

Reliability of 3 Strategies of Orbital Tumor Volume Measurement Using Phantom Modeling

PURPOSE

The reliability of 3 volume measurement strategies was investigated using MRI and a simple method for creating phantom orbit tumors.

METHODS

Water-based starch was molded into orbital "tumors" of 3 shapes (sphere, ovoid, diffuse); water displacement was used to calculate volume. "Tumors" were placed into 3D-printed orbit phantoms, MRIs were obtained and volume analysis was performed. Observers measured tumor volume using ellipsoid volume (EV), manual segmentation, and semi-automated segmentation strategies. Intraclass correlation coefficients were calculated comparing observer measurements to true volumes. The coefficient of repeatability determined the percentage of tumor volume change required for each method to detect tumor growth.

RESULTS

Intraclass correlation coefficients comparing measured volumes to true volumes using EV, manual segmentation, and semi-automated segmentation were 0.61, 0.98, and 0.99 for spherical, 0.64, 0.97, and 0.98 for ovoid, and 0.18, 0.82, and 0.87 for diffuse tumors. Semi-automated segmentation followed by manual segmentation had the highest correlation between measured and true tumor volume for all 3 tumor geometries. EV had low correlation with true volume for all tumor geometries. Diffuse tumors had high variability and low correlation for all 3 measurement techniques.

CONCLUSIONS

This study shows the reliability of 3 strategies to measure orbital tumor volume with MRI based on tumor geometry, using a simple phantom model. EV, the most commonly employed strategy in clinical practice, had low correlation and high variability across tumor shapes. Using manual segmentation and semi-automated segmentation, a measured change in volume greater than 25% may be considered true growth, while the EV strategy required a 40%-400% change in volume to reliably measure tumor growth.

Influence of 4-week or 12-week glucocorticoid treatment on metabolic changes in patients with active moderate-to-severe thyroid-associated ophthalmopathy

Thyroid‐associated ophthalmopathy (TAO) is a serious, progressive, vision‐threatening and difficult‐to‐treat organ‐specific autoimmune disease. The course, therapeutic effects and prognosis of moderate to severe TAO vary greatly. High‐dose intravenous glucocorticoid (IVGC) therapy is considered a first‐line treatment for active moderate‐to‐severe TAO, but there is still insufficient evidence regarding the treatment duration. Long‐term IVGC therapy can influence the metabolism of glucose, lipids, and bone. This study was designed to compare changes in metabolic and immunological indexes as well as the magnetic resonance imaging apparent diffusion coefficient (ADC) of the extraocular muscles after 4 and 12 weeks of IVGC therapy. Forty‐eight patients with active moderate‐to‐severe TAO were included in this retrospective cohort study. Metabolism and immunological indexes were measured before and after therapy. The ADC and clinical activity score (CAS) were used to evaluate the efficacy of treatment in these patients. We found that the patients in the 12‐week group had increased fasting plasma glucose (p = 0.004), glycated hemoglobin (p = 0.028), total cholesterol (p < 0.001), and low‐density lipoprotein (p < 0.001) after therapy. The patients in both groups had reduced bone metabolism markers after therapy. Thyroid peroxidase antibody and thyrotropin receptor antibody levels decreased after treatment in both groups (p < 0.001). A significant decrease in thyroglobulin antibody levels was found in the 4‐week group (p = 0.006). The change in the ADC was higher in the 4‐week group than in the 12‐week group (p = 0.014). However, there were no significant differences in CAS values between the two groups. Therefore, 4‐week IVGC therapy was recommended for patients with TAO with glucose and lipid disorders.

Preliminary evidence of the association between DNAm and orbital volumetry in GO

BACKGROUND

The pathogenesis underlying the alterations of orbital architecture in Graves' orbitopathy (GO) is not yet fully understood. The present study aimed to investigate the association of DNA methylation in peripheral blood and orbital volumetry in Chinese patients with GO.

METHODS

A total of 35 GO subjects (70 orbits) were subjected to computed tomography (CT) scan. The total cross-sectional area of the extraocular muscles (orbital muscles, OM), total orbit area (TOA), and the exophthalmometry were measured, and OM/TOA ratio was calculated. Targeted bisulfite sequencing was performed on seven candidate genes.

RESULTS

No significant correlation was established between the DNA methylation levels of these genes and exophthalmometry. The MBP methylation level was found to be correlated with OM/TOA ratio (P<0.05). Multiple linear regression analysis on parameters, including age, sex, TRAb, duration of GO, and DNA methylation levels of seven genes with OM/TOA ratio confirmed that MBP and OM/TOA ratio had a significant correlation (P<0.05). The partial least squares analysis showed that the top three genes with the highest loadings were MBP, BOLL, and BECN1, and OM/TOA ratio affected the DNA methylation block than exophthalmometry.

CONCLUSIONS

This study provided preliminary evidence that MBP is a potential gene associated with OM enlargement in GO patients according to the combination of DNA methylation sequencing and orbital CT measurement.

Reliability of orbital volume measurements based on computed tomography segmentation: Validation of different algorithms in orbital trauma patients

PURPOSE

To compare the most common methods of segmentation for evaluation of the bony orbit in orbital trauma patients.

MATERIALS AND METHODS

Computed tomography scans (before and after treatment) from 15 patients with unilateral blowout fractures and who underwent orbital reconstructions were randomly selected for this study. Orbital volume measurements, volume difference measurements, prolapsed soft tissue volumes, and bony defect areas were made using manual, semi-automated, and automated segmentation methods.

RESULTS

Volume difference values between intact and damaged orbits after surgery using the manual mode were 0.5 ± 0.3 cm³, 0.5 ± 0.4 cm³ applying semi-automated method, and 0.76 ± 0.5 cm³, determined by automated segmentation (р = 0.216); the mean volumes (MVs) for prolapsed tissues were 3.0 ± 1.9 cm³, 3.0 ± 2.3 cm³, and 2.8 ± 3.9 cm³ (p = 0.152); and orbital wall defect areas were 4.7 ± 2.8 cm², 4.75 ± 3.1 cm², and 4.9 ± 3.3 cm² (p = 0.674), respectively.

CONCLUSIONS

The analyzed segmentation methods had the same accuracy in evaluation of volume differences between two orbits of the same patient, defect areas, and prolapsed soft tissue volumes but not in absolute values of the orbital volume due to the existing diversity in determination of anterior closing. The automated method is recommended for common clinical cases, as it is less time-consuming with high precision and reproducibility.

An accurate interactive segmentation and volume calculation of orbital soft tissue for orbital reconstruction after enucleation

Background

Accurate measurement and reconstruction of orbital soft tissue is important to diagnosis and treatment of orbital diseases. This study applied an interactive graph cut method to orbital soft tissue precise segmentation and calculation in computerized tomography (CT) images, and to estimate its application in orbital reconstruction.

Methods

The interactive graph cut method was introduced to segment extraocular muscle and intraorbital fat in CT images. Intra- and inter-observer variability of tissue volume measured by graph cut segmentation was validated. Accuracy and reliability of the method was accessed by comparing with manual delineation and commercial medical image software. Intraorbital structure of 10 patients after enucleation surgery was reconstructed based on graph cut segmentation and soft tissue volume were compared within two different surgical techniques.

Results

Both muscle and fat tissue segmentation results of graph cut method showed good consistency with ground truth in phantom data. There were no significant differences in muscle calculations between observers or segmental methods (p > 0.05). Graph cut results of fat tissue had coincidental variable trend with ground truth which could identify 0.1cm³ variation. The mean performance time of graph cut segmentation was significantly shorter than manual delineation and commercial software (p < 0.001). Jaccard similarity and Dice coefficient of graph cut method were 0.767 ± 0.045 and 0.836 ± 0.032 for human normal extraocular muscle segmentation. The measurements of fat tissue were significantly better in graph cut than those in commercial software (p < 0.05). Orbital soft tissue volume was decreased in post-enucleation orbit than that in normal orbit (p < 0.05).

Conclusion

The graph cut method was validated to have good accuracy, reliability and efficiency in orbit soft tissue segmentation. It could discern minor volume changes of soft tissue. The interactive segmenting technique would be a valuable tool for dynamic analysis and prediction of therapeutic effect and orbital reconstruction.

T2-relaxation mapping and fat fraction assessment to objectively quantify clinical activity in thyroid eye disease: an initial feasibility study

Imaging in thyroid eye disease (TED) is used to exclude other diagnoses, assess for apical crowding and plan surgery. But to quantify TED activity objectively, subjective clinical scoring assessments remain the norm. Magnetic resonance imaging (MRI) T2-relaxation times correlate with extra-ocular muscle (EOM) inflammation, but are confounded by signal from fat. We investigated whether T2-relaxation mapping in combination with fat fraction (FF) measurements could quantify disease activity in EOMs objectively. Sixty-two TED patients and six controls were enroled for coronal short tau inversion recovery (STIR), T2 multi-echo fast-spin echo and multi-echo fast-gradient echo MRI of the orbits. STIR signal intensity ratios (SIRs), T2-relaxation times and percentage FF were derived for inferior, lateral, superior and medial recti bilaterally. Twelve patients were re-scanned following immunosuppressive treatment. The results found a positive correlation for all subjects between T2 and SIR (p < 0.001), but only mean T2 differed significantly between patients and controls (p < 0.001). We measured FF in EOMs for the first time and found it greater in TED (p < 0.001). There was also a significant reduction in mean T2 after treatment, with a corresponding reduction in the clinical activity score (CAS) in almost all patients. We show that T2-relaxation times differentiate between normal and inflamed EOMs and are responsive to treatment. Combined, uniquely, with FF measurement in EOMs, an objective, quantitative marker of inflammation in TED-affected muscles could be derived. T2-relaxation times mirrored improvements in CAS after treatment, occasionally preceding them. Rarely, they diverged, suggesting limitations in the CAS as a disease burden marker.

Ex vivo orbital volumetry using stereology and CT imaging: A comparison with manual planimetry

OBJECTIVES

To evaluate the applicability of stereology and planimetry in orbital volume measurements using computed tomography (CT) and to compare the results between the two measurements.

METHODS

Experimental study using sheep craniums for CT imaging. Water filling measurements were performed, as the validation technique. Quantification techniques were also evaluated in five human subjects. To examine the proportion of agreement among measurements, we tested intra- and inter-observer agreement.

RESULTS

For stereology customization, a 1/8 systematic sampling scheme was considered as optimal; this resulted in a low coefficient of error (2.59 %) and low measurement time (1.9 mins). In sheep craniums, mean volume measured by water displacement, planimetry and stereology was 17.81 ± 0.59 cm³, 17.87 ± 0.68 cm³ and 17.54 ± 0.49 cm³, respectively. Total volumes, obtained by stereology, were highly correlated with the water-filling method (r=0.893; p = 0.001) and a paired t-test showed significant difference between methods (t=3.047; p = 0.014). Planimetry results displayed a high correlation with the water-filling method (r=0.957; p ≈ 0.001) but no statistically significant difference was found (p = 0.154). Mean difference using planimetry and stereology was 0.332 ± 0.322 cm³. In human subjects, using stereology, the estimated volume ranged between 18.57 cm³ and 19.27 cm³, and the mean orbital volume was 19.05 ± 0.50 cm³ with CE=3.75 ± 0.16 %. Mean measure time was 2.1 ± 0.1 mins.

CONCLUSIONS

Stereological measurements were superior to manual planimetry in terms of user effort and time spent. Stereology sampling of 1/8 was successfully applied in human subjects and yielded a strong correlation with manual planimetry.

KEY POINTS

• Stereology can be applied to measure the orbital volume using computed tomography. • Stereological measurements display high correlation with gold standard planimetry and combine low coefficient of error (2.59%) with low measurement time (1.9 min). • Stereology is superior in terms of user effort and time spent.

Extraocular muscle sampled volume in Graves' orbitopathy using 3-T fast spin-echo MRI with iterative decomposition of water and fat sequences

Background

Current magnetic resonance imaging (MRI) techniques for measuring extraocular muscle (EOM) volume enlargement are not ideally suited for routine follow-up of Graves’ ophthalmopathy (GO) because the difficulty of segmenting the muscles at the tendon insertion complicates and lengthens the study protocol.

Purpose

To measure the EOM sampled volume (SV) and assess its correlation with proptosis.

Material and Methods

A total of 37 patients with newly diagnosed GO underwent 3-T MRI scanning with iterative decomposition of water and fat (IDEAL) sequences with and without contrast enhancement. In each patient, the three largest contiguous coronal cross-sectional areas (CSA) on the EOM slices were segmented using a polygon selection tool and then summed to compute the EOM-SV. Proptosis was evaluated with the Hertel index (HI). The relationships between the HI value and EOM-SV and between HI and EOM-CSA were compared and assessed with Pearson’s correlation coefficient and the univariate regression coefficient. Inter-observer and intra-observer variability were calculated.

Results

HI showed a stronger correlation with EOM-SV (P < 0.001; r = 0.712, r²= 0.507) than with EOM-CSA (P < 0.001; r = 0.645 and r²= 0.329). The intraclass correlation coefficient indicated that the inter-observer agreement was high (0.998). The standard deviation between repeated measurements was 1.9–5.3%.

Conclusion

IDEAL sequences allow for the measurement EOM-SV both on non-contrast and contrast-enhanced scans. EOM-SV predicts proptosis more accurately than does EOM-CSA. The measurement of EOM-SV is practical and reproducible. EOM-SV changes of 3.5–8.3% can be assumed to reflect true volume changes.

Relationship between magnetic resonance imaging signal intensity and volume of extraocular muscles in thyroid-associated ophthalmopathy with methylprednisolone pulse therapy

Purpose

To characterize the relationship between inflammation and swelling of extraocular muscles in thyroid-associated ophthalmopathy before and after methylprednisolone pulse therapy.

Methods

The signal intensities and volumes of the superior rectus (SR), inferior rectus (IR), lateral rectus (LR), medial rectus (MR), and superior oblique (SO) muscles were measured with magnetic resonance imaging in 25 eyes of 25 patients with thyroid-associated ophthalmopathy in the acute inflammatory phase before and after methylprednisolone pulse therapy. The signal intensity ratios (SIRs) of muscles and brain white matter were calculated.

Result

The mean SIRs before treatment were 2.28±0.74 in SR, 2.66±0.57 in IR, 2.03±0.42 in LR, 2.45±0.49 in MR, and 1.98±0.48 in SO muscles. The mean SIRs after treatment were 1.82±0.62, 1.84±0.52, 1.70±0.35, 1.95±0.46, and 1.60±0.36, respectively. The mean volumes (cm³) before treatment were 1.35±0.67 in SR, 1.21±0.39 in IR, 0.66±0.13 in LR, 0.94±0.31 in MR, and 0.58±0.14 in SO muscles. Those after treatment were 1.12±0.45, 0.91±0.31, 0.61±0.12, 0.85±0.28, and 0.49±0.11, respectively. The SIRs showed significantly positive correlations with volumes both before and after treatment in SR muscles (before, r=0.77; after, r=0.69), IR muscles (before, r=0.65; after, r=0.60), MR muscles (before, r=0.69; after, r=0.73), and SO muscles (before, r=0.52; after, r=0.50) (P<0.01 for all correlations).

Conclusion

Swelling reflected the inflammation in extraocular muscles of thyroid-associated ophthalmopathy both before and after treatment.

Computed tomographic measurements of orbital entrance dimensions in relation to age and gender in a sample of healthy Iranian population

PURPOSE

To determine the dimensions of orbital entrance in unaffected bony orbit by computed tomography (CT) in a sample of Iranian population.

METHODS

Radiologic features of 120 patients were gathered using standardized skull protocol by CT scan. We measured the distance between anterior lacrimal crest and orbital border of zygomatic bone, termed width, and the distance between the plane passing through the anterior orbital entrance to optic canal, termed depth, using horizontal sections of skull base CT scan. Sagittal sections were used to demonstrate the height, the distance between frontal and maxillary bone. Orbital index (height/width *100) was then calculated.

RESULTS

The mean values of orbital width, height, and depth were 28.49 ± 2.35 mm, 32.14 ± 1.57 mm, and 38.84 ± 3.90 mm, respectively. There was a significant difference in height (P = 0.001), depth (P = 0.004), and width (P = 0.012) between the right and left orbits. The mean value of the orbital index was 88.65 ± 8.90 mm in this population.

CONCLUSIONS

The orbital index of this sample Iranian people is Mesoseme according to our study results, the expected characteristic of the white race. The right orbits are determined to be larger than the left ones.

Correlation between Extraocular Muscle Size Measured by Computed Tomography and the Vertical Angle of Deviation in Thyroid Eye Disease

The aim of this study was to investigate extraocular muscle (EOM) volume and cross-sectional area using computed tomography (CT), and to determine the relationship between EOM size and the vertical angle of deviation in thyroid eye disease (TED). Twenty-nine TED patients (58 orbits) with vertical strabismus were enrolled in the study. All patients underwent complete ophthalmic examination including prism, alternate cover, and Krimsky tests. Orbital CT scans were also performed on each patient. Digital image analysis was used to quantify superior rectus (SR) and inferior rectus (IR) muscle cross-sectional areas and volumes. Measurements were compared with those of controls. The correlation between muscle size and degree of vertical angle deviation was evaluated. The mean vertical angle of deviation was 26.2 ± 4.1 prism diopters. The TED group had a greater maximum cross-sectional area and EOM volume in the SR and IR than the control group (all p<0.001). Area and volume of the IR were correlated with the angle of deviation, but the SR alone did not show a significant correlation. The maximum cross-sectional area and volume of [Right IR + Left SR − Right SR − Left IR] was strongly correlated with the vertical angle of deviation (P<0.001). Quantitative CT of the orbit with evaluation of the area and volume of EOMs may be helpful in anticipating and monitoring vertical strabismus in TED patients.

Orbital volume analysis: validation of a semi-automatic software segmentation method

Purpose

The purpose of this study was to validate a quick, accurate and reproducible (semi-) automatic software segmentation method to measure orbital volume in the unaffected bony orbit. Precise volume measurement of the orbital cavity is a useful addition to pre-operative planning and intraoperative navigation in orbital reconstruction.

Methods

In 21 CT scans, one unaffected orbit was selected to compare manual segmentation (gold standard) with three segmentation methods using iPlan software (version 3.0.5; Brainlab, Feldkirchen, Germany): automatic (method A), automatic minus bone/air masks (method SA) and automatic minus masks followed by manual adjustments (method SAA). First, validation of the manual segmentation and a newly described method for the anterior boundary was performed. Subsequently the accuracy, reproducibility and time efficiency of the methods were examined. Measurements were performed by two observers.

Results

The intraclass correlation for the interobserver agreement of the anterior boundary was 0.992, and the intraobserver and interobserver agreement for the manual segmentation were 0.997 and 0.994, respectively. Method A had an average volumetric difference of 0.49 cc (SD 0.74) in comparison with the gold standard; this was 0.24 cc (SD 0.27) for method SA and 0.86 cc (SD 0.27) for method SAA. The average time for each method was 38 (SD 5.4), 146 (SD 16.0) and 327 (SD 36.2) seconds per orbit.

Conclusion

The built-in automatic method A is quick, but suboptimal for clinical use. The newly developed method SA appears to be accurate, reproducible, quick and easy to use. Manual adjustments in method SAA are more time-consuming and do not improve volume accuracy. The largest volume discrepancy is located near the inferior orbital fissure.

Graves' ophthalmopathy: the role of diffusion-weighted imaging in detecting involvement of extraocular muscles in early period of disease

OBJECTIVE

To evaluate involvement of the extraocular muscle (EOM) using diffusion-weighted imaging (DWI), to determine whether there is correlation with conventional orbital MRI and apparent diffusion coefficient (ADC) values in patients with Graves' ophthalmopathy (GO).

METHODS

35 patients known clinically with GO and 21 healthy controls were studied. Patients were assessed with clinical activity scores. All subjects underwent conventional MRI and DWI study. Involvement of the EOM was evaluated. The patients were classified as involved or uninvolved on orbital MRI and their ADC values in DWI compared.

RESULTS

There was significant difference in the mean ADC value of all the EOMs in patients vs controls. The ADC values of all the EOMs were higher in patients. There were significant differences in ADC values between uninvolved muscles on conventional MRI and controls for the MR, SR and LR. There was no significant difference in ADC value between the two groups when considering the IR. ADC values of medial, lateral and superior rectus muscles were increased.

CONCLUSION

Increased ADC values of the EOM in patients with GO suggest that EOM damage begins at a very early stage before being detected on routine orbital MRI. The routine MRI with DWI sequence will be a useful adjunct in the selection of a group of patients most likely to benefit from early treatment.

ADVANCES IN KNOWLEDGE

This study can help to evaluate the involvement of GO in early period with MRI added DWI.

Robust optic nerve segmentation on clinically acquired computed tomography

The optic nerve (ON) plays a critical role in many devastating pathological conditions. Segmentation of the ON has the ability to provide understanding of anatomical development and progression of diseases of the ON. Recently, methods have been proposed to segment the ON but progress toward full automation has been limited. We optimize registration and fusion methods for a new multi-atlas framework for automated segmentation of the ONs, eye globes, and muscles on clinically acquired computed tomography (CT) data. Briefly, the multi-atlas approach consists of determining a region of interest within each scan using affine registration, followed by nonrigid registration on reduced field of view atlases, and performing statistical fusion on the results. We evaluate the robustness of the approach by segmenting the ON structure in 501 clinically acquired CT scan volumes obtained from 183 subjects from a thyroid eye disease patient population. A subset of 30 scan volumes was manually labeled to assess accuracy and guide method choice. Of the 18 compared methods, the ANTS Symmetric Normalization registration and nonlocal spatial simultaneous truth and performance level estimation statistical fusion resulted in the best overall performance, resulting in a median Dice similarity coefficient of 0.77, which is comparable with inter-rater (human) reproducibility at 0.73.

Evaluation of Multi-Atlas Label Fusion for In Vivo MRI Orbital Segmentation

Multi-atlas methods have been successful for brain segmentation, but their application to smaller anatomies remains relatively unexplored. We evaluate 7 statistical and voting-based label fusion algorithms (and 6 additional variants) to segment the optic nerves, eye globes and chiasm. For non-local STAPLE, we evaluate different intensity similarity measures (including mean square difference, locally normalized cross correlation, and a hybrid approach). Each algorithm is evaluated in terms of the Dice overlap and symmetric surface distance metrics. Finally, we evaluate refinement of label fusion results using a learning based correction method for consistent bias correction and Markov random field regularization. The multi-atlas labeling pipelines were evaluated on a cohort of 35 subjects including both healthy controls and patients. Across all three structures, NLSS with a mixed weighting type provided the most consistent results; for the optic nerve NLSS resulted in a median Dice similarity coefficient of 0.81, mean surface distance of 0.41 mm and Hausdorff distance 2.18 mm for the optic nerves. Joint label fusion resulted in slightly superior median performance for the optic nerves (0.82, 0.39 mm and 2.15 mm), but slightly worse on the globes. The fully automated multi-atlas labeling approach provides robust segmentations of orbital structures on MRI even in patients for whom significant atrophy (optic nerve head drusen) or inflammation (multiple sclerosis) is present.

Magnetic resonance imaging with diffusion-weighted imaging in the evaluation of thyroid-associated orbitopathy: getting below the tip of the iceberg

OBJECTIVES

To compare extraocular muscles (EOMs) T2, post-contrast T1 (T1Gad) signal intensity ratios (SIRs) and normalized-apparent diffusion coefficient (n-ADC) values in patients with thyroid-associated orbitopathy (TAO) at different phases of activity and severity and correlate MRI modifications to clinical evolution during follow-up.

METHODS

A total of 74 TAO patients were classified as active or inactive on the basis of the clinical activity score (CAS). Severity of EOM impairment was evaluated by assigning a functional score to each rectus. T2, T1Gad SIRs and n-ADC of EOMs were compared in patients with active inflammation, those with inactive disease and 26 healthy controls, and correlated with clinical scores. MRI parameter variation was correlated with clinical modifications during follow-up.

RESULTS

All MRI parameters in TAO EOMs were significantly higher than in healthy subjects and correlated with muscle dysfunction and CAS. EOMs of active patients showed higher T2 and T1Gad SIRs than those with inactive disease. The T2 SIR and n-ADC of normally functioning TAO EOMs were higher than those of healthy controls. SIRs decreased in clinically improved and clinically stable EOMs after therapy.

CONCLUSIONS

T2 SIR, T1Gad SIR and n-ADC are objective measures of activity and severity of EOMs in TAO patients. MRI shows clinically silent muscle involvement and modifications.

KEY POINTS

• MRI and DWI measures are objective, quantitative parameters of TAO activity and severity • MRI and DWI measures significantly correlate with clinical scores in TAO patients • MRI and DWI can identify clinically silent inflammation of deep orbital structures • MRI and DWI can depict subclinical modifications during follow-up • MRI and DWI may aid clinicians in choosing the most appropriate treatment.

Correlation between magnetic resonance imaging and ultrasound measurements of eye muscle thickness in thyroid-associated orbitopathy

AIMS

To compare ultrasound (US) and magnetic resonance imaging (MRI) measurements of horizontal eye muscle thickness in patients with thyroid-associated orbitopathy (TAO) and to compare these measurements according to the phase of the disease, the severity of exophthalmos, and the experience of the investigator.

METHODS

A total of 180 orbits of adult patients with TAO were investigated from May 2007 to December 2012. In addition to their general ophthalmic examination, all patients underwent ultrasonographic measurement of horizontal eye muscle thickness with the B-scan technique and MRI examination of the orbit. Correlations between values obtained by US and MRI were determined for different subgroups according to disease activity (active, inactive), exophthalmos values (Hertel < 18 mm; Hertel 18-22 mm; Hertel > 22 mm), and the time period of examination (2007-2009; 2010-2012).

RESULTS

Positive moderate correlation between US and MRI values for the medial rectus muscle (MRM; r = 0.690) and for the lateral rectus muscle (LRM; r = 0.572) was found. Significantly higher correlation was found for the MRM (P < 0.0001) and the LRM (P = 0.0008) in the time period 2010-2012 than in that of 2007-2009. Increasing correlation was found for MRM with increasing values of exophthalmos but this increase was not statistically significant. In the active phase of the disease compared to the inactive phase, statistically significant increased correlation (P = 0.019) was found for the LRM.

CONCLUSIONS

Ultrasonographic measurement of horizontal eye muscles thickness in TAO moderately correlates with values obtained using MRI. The accuracy of ultrasonographic measurements in particular increases with the experience of the investigator.

Differential involvement of orbital fat and extraocular muscles in graves' ophthalmopathy

Graves' ophthalmopathy (GO) is characterized by swelling of orbital fat and extraocular muscles, but little attention has been given to differential involvement of fat and muscles. Advancements in imaging allow rather accurate measurements of orbital bony cavity volume (OV), fat volume (FV) and muscle volume (MV), and are the topics of this review. Ratios of FV/OV and MV/OV neutralize gender differences. In adult Caucasian controls, mean values ± SD of FV/OV are 0.56 ± 0.11 and of MV/OV are 0.15 ± 0.02. FV increases substantially and MV decreases slightly with advancing age, requiring age-specific reference ranges. In 95 consecutive untreated Caucasian GO patients, both FV and MV were within normal limits in 25%, increased FV but normal MV was present in 5%, normal FV but increased MV was detected in 61%, and both increased FV and MV was evident in 9%. Increased FV was associated with more proptosis and longer GO duration. Increased MV was associated with older age, more severe GO (more proptosis and diplopia, worse eye muscle ductions), higher TBII and current smoking. At the cellular and molecular level differential involvement of fat and muscles might be related to differences between fibroblast phenotypes and cytokine profiles in each compartment, to different orbital T cell subsets during the course of the disease and to peroxisome proliferator activator receptor-γ polymorphisms and modulation of 11β-hydroxysteroid dehydrogenase-1. Enlarged muscles are apparently a rather early phenomenon in GO, whereas increases in fat mass occur relatively late. Why a minor subset of GO patients presents with an increase of only fat remains poorly understood.

A quantitative method for assessing the degree of axial proptosis in relation to orbital tissue involvement in Graves' orbitopathy

PURPOSE

To define a method of quantifying axial proptosis in patients with Graves' orbitopathy (GO) and to validate a score that correlates with the orbital involvement and helps determine the degree of proptosis correction for elective orbital decompression.

DESIGN

Retrospective, case series.

PARTICIPANTS

The study included 50 patients (group A) and 29 control subjects who underwent orbital computed tomography (CT). The method was then validated in another group of 21 patients with GO (group B).

METHODS

The orbital area (OA) was measured manually on the central axial section of the CT scan at a level where the lens is visualized. The OA intersects the projection of the globe and delimitates the chord of an arch (globe chord [OC]). The area of the circular sector under the chord (CA) represents the portion of the globe within the orbit.

MAIN OUTCOME MEASURES

A CA-to-OA ratio was calculated to reduce the error due to variability of the measurements and to perform correlations with some of the clinical parameters of GO.

RESULTS

Measurement error was low (<2%). We did not observe significant differences in the mean OA of patients with GO (783.6 ± 12.1 mm(2)) and controls (758.5 ± 20.4 mm(2); P = not significant). The OC value in patients with GO was 130.2 ± 11.5 mm(2), significantly lower than in controls (281.8 ± 9.7 mm(2); P<0.0001). The CA-to-OA ratio also was lower in patients with GO than in controls (0.16 ± 0.01 vs. 0.38 ± 0.01; P<0.0001). A significant correlation was found in patients with GO between the CA-to-OA ratio and proptosis (P<0.001), lid fissure (P = 0.004), and intraocular pressure (P<0.001). In group B, the CA-to-OA ratio was 0.18 ± 0.02, significantly different from that of controls (P<0.0001) and inversely correlated with proptosis (P<0.0001) and lid fissure (P<0.045).

CONCLUSIONS

By measuring the CA-to-OA ratio, we were able to quantify the degree of axial proptosis in patients with GO. The significant correlation of CA/OA with some orbital parameters confirms that this parameter also may be used as a measure of orbital involvement in GO.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

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.

Predicting dysthyroid optic neuropathy using computed tomography volumetric analyses of orbital structures

OBJECTIVE

To evaluate the ability of orbital apex crowding volume measurements calculated with multidetector-computed tomography to detect dysthyroid optic neuropathy.

METHODS

Ninety-three patients with Graves' orbitopathy were studied prospectively. All of the patients underwent a complete neuro-ophthalmic examination and computed tomography scanning. Volumetric measurements were calculated from axial and coronal contiguous sections using a dedicated workstation. Orbital fat and muscle volume were estimated on the basis of their attenuation values (in Hounsfield units) using measurements from the anterior orbital rim to the optic foramen. Two indexes of orbital muscle crowding were calculated: i) the volumetric crowding index, which is the ratio between soft tissue (mainly extraocular muscles) and orbital fat volume and is based on axial scans of the entire orbit; and ii) the volumetric orbital apex crowding index, which is the ratio between the extraocular muscles and orbital fat volume and is based on coronal scans of the orbital apex. Two groups of orbits (with and without dysthyroid optic neuropathy) were compared.

RESULTS

One hundred and two orbits of 61 patients with Graves' orbitopathy met the inclusion criteria and were analyzed. Forty-one orbits were diagnosed with Graves' orbitopathy, and 61 orbits did not have optic neuropathy. The two groups of orbits differed significantly with regard to both of the volumetric indexes (p<0.001). Although both indexes had good discrimination ability, the volumetric orbital apex crowding index yielded the best results with 92% sensitivity, 86% specificity, 81%/94% positive/negative predictive value and 88% accuracy at a cutoff of 4.14.

CONCLUSION

This study found that the orbital volumetric crowding index was a more effective predictor of dysthyroid optic neuropathy than previously described computed tomography indexes were.

A three-dimensional construct of the aging eyebrow: the illusion of volume loss

BACKGROUND

The eyebrows and eyebrow fat pads, key structures in upper facial aesthetics, are particularly vulnerable to age-related changes.

OBJECTIVES

In this study, the authors compare the impact of aging on the eyebrows and eyebrow fat pad volume in men and women through three-dimensional (3D) volumetric analysis.

METHODS

Electronic medical records of patients seen at the Jules Stein Eye Institute in the Division of Orbital and Ophthalmic Plastic Surgery between 2005 and 2010 were reviewed. Patients were included if they had undergone investigative imaging of the orbit for unilateral pathology. Computed tomography (CT) scans of patients with Graves disease diagnosis, extensive orbital trauma, and/or previous eyebrow surgery were excluded. A total of 52 CT scans (24 men and 28 women) were retained for analysis. A 3D reconstruction software was used to analyze the scans and calculate volumes of the retroorbicularis oculi fat (ROOF), galeal fat (ROOF and subcutaneous fat), and soft tissue muscles.

RESULTS

Galeal and brow fat volumes showed a significant positive trend toward enlargement in women (P values of .01 and .05, respectively). Although men showed a tendency toward fat enlargement with age, this was not statistically significant. Soft tissue-muscle volume decreased significantly in aging women (9.32 mm(3)/y) (P = .02). Data indicated that soft tissue volume in men tended to increase with age (3.92 mm(3)/y) but not significantly (P = .36). Neither total volume nor brow thickness appeared to change significantly in women (P = .56, P = .73). In men, total volume and brow thickness showed weak evidence of increasing with age (P = .12, P = .22). Linear regressions of Hertel measurements with and without sex interaction showed no statistically significant trend between the amount of proptosis and the galeal or brow fat.

CONCLUSIONS

Although overall eyebrow volume does not change with age, the relative contribution of fat and soft tissue to the total volume does seem to change. This pattern also differs between males and females. As women age, the fat volume increases and the soft tissue volume decreases. In men, the shift from soft tissue volume to fat volume is less pronounced. Although many clinicians have been drawn to the concept of fat volume deflation as a key element of facial aging, this study does not support this perspective in the eyebrow fat pad. An increasingly refined understanding of the dynamics of facial aging is mandatory for clinical diagnosis and will likely provide the framework from which to develop more innovative treatment options.

[Short-tau inversion-recovery (STIR) sequence magnetic resonance imaging evaluation of orbital structures in Graves' orbitopathy]

OBJECTIVE

To evaluate the orbital structures and to establish correlations with disease activity and severity in patients with Graves' hyperthyroidism and orbitopathy (GO) using short-tau inversion-recovery (STIR) sequence magnetic resonance imaging (MRI).

METHODS

Observational, cross-sectional, case-control study. Twenty-eight patients with euthyroid status after treatment and GO (GO group) and 15 control subjects (control group) were included. Patients underwent a complete ophthalmologic examination and were then assessed according to the EUGOGO (European Group on Graves' Orbitopathy) recommendations. Muscle cross-sectional areas, orbital tissue volumes and the signal intensity ratio (SIR) from the most inflamed extraocular muscle were calculated using a STIR-T2 weighted sequence MRI. Correlations between clinical and MRI measurements were analyzed.

RESULTS

Enlargements in the cross-sectional areas and volumes were significant for most EOMs (P<.001), but not for the lateral rectus muscle cross-sectional area. A significant difference in SIR values between patients with GO and control subjects (P<.001) was found. No significant correlations were found between muscle cross-sectional areas, orbital tissue volumes, SIR values and the clinical activity parameters.

CONCLUSIONS

Given the small sample size of our study, with the obvious need for larger clinical trials, we were unable to demonstrate that the STIR sequences in MRI are a sensitive tool in assessing patients with longstanding GO in order to detect inflammatory changes and activity follow-up, possibly because it is in inactive phase. Meanwhile, it is still necessary to continue performing a thorough clinical evaluation in the therapeutic management of GO.

Correlation between extraocular muscle size and motility restriction in thyroid eye disease

PURPOSE

Evaluate the relationship between extraocular muscle (EOM) size, measured by computed tomography, and ocular motility in thyroid eye disease (TED).

METHODS

This case series is based on a retrospective review of the records of 54 patients (108 orbits) with TED. Main outcome measures included EOM size and degree of motility restriction. The average diameter of each rectus muscle was compared with published norms. Four subpopulations based on Age (< 40 or ≥ 40 years) and State of thyroid eye disease (active or stable) were studied. Versions were measured by the corneal light reflex method. The trend of muscle diameter versus motility restriction was evaluated.

RESULTS

The average EOM diameter was greater than the norm in the study cohort and 4 subpopulations. The average diameter was largest in the Older and Active TED subpopulations. The inferior rectus and medial rectus were most frequently restricted in the study cohort and 4 subpopulations. The medial rectus had the strongest trend between increasing diameter and motility restriction, followed by the inferior rectus and the superior muscle group (comprised of the superior rectus and levator palpebrae superioris). However, there was a general lack of strong correlation between the diameter of the rectus muscles and their respective motility, especially in the Younger subpopulation.

CONCLUSION

EOM diameters are larger and have more restricted motility in the Older and Active TED subpopulations. Contrary to prior publications, the correlation between EOM diameters and motility was weak, especially in the Younger subpopulation. These findings suggest that the pathophysiology of EOM enlargement is different based upon the age of the patient and the activity of the orbitopathy.