Measurement of Intra-Orbital Structures in Normal Chinese Adults Based on a Three-Dimensional Coordinate System

A novel method of measuring proptosis with computed tomography

BACKGROUND

Computed tomography (CT) can avoid interference factors and has been imported into some software to measure proptosis clinically as the golden standard.

PURPOSE

To establish a new method for semi-automatically measuring the proptosis on CT and evaluate its accuracy and reproducibility.

MATERIAL AND METHODS

A total of 50 orbital CT images were collected of healthy individuals, 25 patients with Graves ophthalmopathy (GO), and 25 patients with orbital fracture (OF). A new image processing software, MedrawHDC, was developed to semi-automatically measure the proptosis (MedrawHDC method). The classic radiological (CR) method (measuring proptosis with the software called Mimics) and MedrawHDC method were applied in all three groups (measured by observer S). Hertel's exophthalmometer (HE) method was also applied in the GO group. Moreover, two other observers were asked to measure the proptosis using MedrawHDC, to evaluate its reproducibility.

RESULTS

The MedrawHDC method was highly consistent with the CR method in measuring proptosis (normal group: intraclass correlation coefficient [ICC] = 0.989; GO group: ICC = 0.979; OF group: ICC = 0.979). In the GO group, the value of proptosis measured by two radiological methods were consistent with that measured by the HE method (CR method: ICC = 0.703; MedrawHDC method: ICC = 0.697). Bland-Altman plots showed similar results. The measurements obtained by three observers were highly reproducible (ICC = 0.995).

CONCLUSION

The newly established MedrawHDC method, with high accessibility, convenience, and repeatability, is reliable in assessing proptosis. It shows high potential for wide application, having clinical value for scientific evaluation of proptosis.

Prediction of exophthalmos by body mass index for craniofacial reconstruction: consequences for cold cases

It is inconvenient for a forensic practitioner to gather population-specific data before performing a facial reconstruction. The inconvenience may defeat the point of creating the reconstruction. The objective of this study was to evaluate a non-population-dependent method of determining exophthalmos. The protrusion of the eyeball is known to vary with the contents of the orbital cavity based on bony orbital resorption or increased or decreased fat contents, as well as according to relative eyeball size. Of use are available statistics on body mass index, and this is discussed within the context of eyeball protrusion. A weak positive correlation (0.3263) between the body mass index of the country where the study originated, and the degree of exophthalmos was found. The results suggest that eyeball protrusion rates can be established according to body mass index, and this framework may be more useful considering conventional police practices.

Normative orbital measurements in an Australian cohort on computed tomography

PURPOSE

To determine the normal diameters of the extraocular muscles (EOMs) and optic nerve sheath complex (ONSD) and correlate with patient demographics in an Australian cohort.

METHODS

Consecutive patients who underwent contrast enhanced computed tomography (CT) orbits between December 2017 and March 2021 were included. Patients with bilateral disease, previous orbital surgery, or poor scan quality were excluded. Normal orbit was used in patients with unilateral orbital disease.

RESULTS

Two hundred one orbits from 201 patients were included. Normal measurements (mean ± SD) were as follows: medial rectus (MR) 4.22 ± 0.56 mm; inferior rectus (IR) 4.20 ± 0.70 mm; lateral rectus (LR) 3.40 ± 0.56 mm; superior muscle group (SMG) 4.13 ± 0.72 mm; superior oblique (SO) 2.60 ± 0.43 mm; inferior oblique (IO) on quasi-sagittal plane 2.19 ± 0.42 mm, and the ONSD 5.62 ± 0.82 mm. The mean diameters of the LR, SMG, IR, SO, and ONSD were significantly larger in male than female patients (p < .05). Statistically significant correlation was found between age and the diameters of the LR (r = 0.29, p < .01), SMG (r = 0.22, p < .01), IO on a coronal plane (r = -0.18, p < .01), and ONSD (r = 0.16, p = .02).

CONCLUSION

This normative data may be used to diagnose pathological enlargement of the optic nerve and extraocular muscles, including involvement of the oblique muscles.

Orbital MRI 3D Reconstruction Based on Volume Rendering in Evaluating Dysthyroid Optic Neuropathy

PURPOSE

To perform orbital magnetic resonance imaging (MRI) three-dimensional (3D) reconstruction based on volume rendering and analyse changes in soft tissues in dysthyroid optic neuropathy (DON) patients.

METHODS

Using MRI 3D reconstruction based on volume rendering, orbital model parameters were compared with measurements made by observers. The fat volume (FV) and extraocular rectus muscle volume (EOMV) of subjects were calculated via MRI 3D reconstruction. Visual functions were assessed for all thyroid-associated ophthalmology (TAO) patients. Receiver operating characteristic (ROC) curves were analysed to evaluate DON in soft tissues. Correlations between visual function parameters and 3D reconstruction measurement were analysed.

RESULTS

All interclass correlation coefficients between the 3D reconstruction and observer measurements were above 0.950. A total of 21 healthy orbits, 38 TAO orbits without DON and 23 TAO orbits with DON were studied. The FV and EOMV were greater in the DON group than in the healthy and non-DON groups (all p < 0.05). EOM enlargement contributed the most to the DON (odds ratio = 2.79, 95% confidence interval = 1.53, 5.07). The areas under the ROC curves of the reconstruction measurements were as follows: EOMV, 0.850; FV, 0.674; whole volume, 0.726; and EOMV/FV, 0.712. Visual function impairment was positively associated with EOM enlargement. When the EOMV was above 4.035 ml, the occurrence of DON was probable.

CONCLUSIONS

MRI 3D reconstruction based on volume rendering is a reliable method for analysing orbital soft tissues. A larger the EOMV was the most relevant factor in DON.

Normative measurements of the superior oblique and inferior oblique muscles by magnetic resonance imaging

Purpose

Normative oblique muscle data may help to diagnose pathological enlargement of the oblique muscles. We aim to describe the normative values of the superior and inferior oblique muscles in an Australian cohort on T1-weighted MRI and fat suppressed contrast enhanced T1-weighted MRI.

Methods

A retrospective review of patients who underwent 3 T orbital MRI. The healthy orbits were used to conduct measurements in patients with a unilateral orbital lesion. The maximum diameters of the superior and inferior oblique muscles were measured on coronal planes. The diameter was measured perpendicular to the long axis of the muscles.

Results

The normal measurements (mean ± SD) on fat suppressed contrast enhanced T1-weighted MRI: superior oblique, 3.0 ± 0.5 mm and inferior oblique, 2.7 ± 0.5 mm. On T1-weighted MRI: superior oblique, 2.8 ± 0.5 mm and inferior oblique, 2.5 ± 0.4 mm. In patients who had both sequences performed, the superior and inferior oblique diameters were significantly higher on the fat suppressed contrast-enhanced T1-weighted MRI than the T1-weighted MRI sequence (p < 0.01).

Conclusion

Oblique muscle enlargement may be seen in a range of orbital diseases. These data may help in diagnosing oblique muscle enlargement. In addition, variations in the measured muscle diameters can be seen according to the scan sequence that is used.

Differences in anthropometric measures of the orbit between Serbian and Roma populations of the Central Serbia

Introduction/Objectives. The shape and size of the orbital cavity are important parameters in planning surgical interventions and have significance in anthropology and forensic medicine. The aim of this study was to determine the morphometric characteristics of orbital cavity in Serbian population and to examine if there are differences in examined parameters between Serbs and the Roma Community of Serbia. Methods. Using computer tomography and subsequent multiplanar reconstruction we analyzed orbits from 76 Serbian and 18 Roma healthy volunteers. There was no significant difference in age between the ethnicities. Results. The height and width of the left orbit and the height of the right orbit were significantly higher in Roma group, whereas the width of the right orbit was not statistically different between ethnicities. Orbital indices, however, for both left and right orbit did not significantly differ between Serbian and Roma examinees. Right orbital volume did not differ between the groups, but left orbits had significantly larger volumes in Roma population. Finally, biorbital and interorbital width were both significantly higher in Roma than in Serbian examinees. We could not show differences between sexes except for the biorbital width, which had lower values in Serbian, but not Roma women than in men. Conclusion. Taken together, our results indicate larger orbits, as well as greater distances between the eyes in Roma than in Serbian examinees.

In Search of Excellence: From a Small Clinical Unit to an Internationally Recognized Center for Orbital Diseases Research and Surgery at the Department of Ophthalmology, Shanghai Ninth People's Hospital, China

ABSTRACT

"Where there is a will, there is a way." It is never easy to make progress and development but with full dedication and firm commitment, many aspirations can still be realized. We would like to share with the readers the story of how we develop our division of orbital diseases and surgery from scratch to strengths over a period of 2 decades at the Department of Ophthalmology of Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, China.

Automatic orbital computed tomography coordinating method and quantitative error evaluation based on signed distance field

BACKGROUND

Orbital computed tomography (CT) is commonly used for the diagnosis and digital evaluation of orbital diseases. Yet, this approach requires longer scanning time, increased radiation exposure, and, especially, difficult patient positioning that can affect judgment and data processing. According to high-quality research on orbital imaging, computer-assisted surgery, and artificial intelligent diagnostic development, the correction of a coordinate system is a necessary procedure. Nevertheless, existing manual calibration methods are challenging to reproduce and there is no objective evaluation system for errors.

PURPOSE

To establish a method for automatic calibration of orbital CT images and implementation of quantitative error evaluation.

MATERIAL AND METHODS

A standard three-dimensional (3D) orbit model was manually adjusted, and optimized orbital models were reconstructed based on the initial registration of the skull-bound directed bounding box and the registration of the mutual information method. The calibration error was calculated based on the signed distance field. Seventeen cases of orbital CT were quantitatively evaluated.

RESULTS

A new method for automatic calibration and quantitative error evaluation for orbital CT was established. The calibrated model error with ±2 mm accounted for 81.61% ± 6.91% of the total models, and the error of ±1 mm accounted for 53.49% ± 7.07% of the total models.

CONCLUSION

This convenient tool for orbital CT automatic calibration may promote the related quantitative research based on orbital CT. The automated operation and small error are beneficial to the popularization and application of the tool, and the quantitative evaluation facilitates other coordinate systems.

Prediction of late displacement of the globe in orbital blowout fractures

PURPOSE

To establish a linear measuring method in computed tomographic (CT) images to predict the displacement of the globe late after orbital blowout fracture.

METHODS

Subjects were retrospectively included. Inclusion criteria were as follows: (1) adult subjects (≥18 years old at the time of trauma); (2) unilateral orbital medial-wall and/or floor fractures; (3) CT examination at least 30 days after trauma. Exclusion criteria were as follows: (1) facial or orbital fracture extending to other parts of the orbit than medial-wall and/or floor; (2) history of orbital or ocular abnormality other than the orbital trauma; (3) severe ocular trauma accompanied by the orbital trauma; (4) orbital fracture treated surgically before the CT examination. A co-ordinate system was built based on the orbital CT scans. Displacements of orbital walls, displacement of the globe and relative location of the fracture site were measured. Correlations between the variables were investigated.

RESULTS

Ninety-nine per cent of fracture sites of the medial wall and 100% of fracture sites of the floor were posterior to the centre of the unaffected globe. The affected globe moved significantly medially (p < 0.001) and backwards (p < 0.001) in pure medial-wall fracture; backwards (p < 0.001) and downwards (p = 0.017) in pure floor fracture; and medially (p < 0.001), backwards (p < 0.001) and downwards (p < 0.001) in medial-wall and floor fractures. Displacement of the globe was correlated with displacements of the orbital walls, and the regression formulae were therefore fitted. Application of the formulae revealed that the same extent of orbital wall displacement caused more displacement of the globe in female patients than in male patients.

CONCLUSIONS

A linear measuring method in a three-dimensional co-ordinate system was established to identify the displacements of orbital walls and the displacement of the globe in orbital blowout fractures. The regression formulae generated in this study might be used in clinical practice to predict late displacement of the globe by measuring the displacements of orbital walls.