Interzygomatic Line Research Articles

A Hypothesis for the Pathologic Mechanism of Idiopathic Exophthalmos Based on Computed Tomographic Evaluations.

The causes of idiopathic exophthalmos were still unknown. We used computed tomography to compare the orbital structures of patients with idiopathic exophthalmos and those of a healthy Japanese population. A total of 18 orbits (ranged 17-52 years) in idiopathic exophthalmos and 334 normal orbits (ranged 17-59 years) were included. On computed tomography, the eyeball and orbit sizes, lateral wall thickness and length, perpendicular distance from the interzygomatic line to the medial orbital rim, and the nasal cavity width were measured. No significant differences in eyeball or orbit sizes were found between the idiopathic exophthalmos and control groups (P > 0.05). In contrast, the mean lateral wall thickness of the idiopathic exophthalmos group was significantly thicker than that of the control group (P < 0.01). The lateral wall length was shorter with significant difference (P < 0.05). The perpendicular distance and the width of the nasal cavity in the idiopathic exophthalmos group were longer with significant difference (P < 0.05). The cause of idiopathic exophthalmos is compression of orbital contents by the medial wall expansion. The force of expansion of medial wall also influences the zygoma according to Wolff law.

English

Thyroid-associated orbitopathy (TAO), frequently termed Graves ophthalmopathy, is part of an autoimmune process that can affect the orbital and periorbital tissue, the thyroid gland, and, rarely, the pretibial skin or digits (thyroid acropachy), Although the use of the term thyroid ophthalmopathy is pervasive, the disease process is actually an orbitopathy in which the orbital and periocular soft tissues are primarily affected with secondary effects on the eye. Thyroid orbitopathy (TO) is most prevalent among females in the fourth and fifth decades and is usually associated with thyroid dysfunction. Thyroid-associated orbitopathy may precede, coincide, or follow the systemic complications of dysthyroidism. The ocular manifestations of thyroid-associated orbitopathy include eyelid retraction, proptosis, chemosis, periorbital edema, and altered ocular motility with significant functional, social, and cosmetic consequences. we describe a unique case of unilateral exophthalmos in a young male patient. REPORT OF A CASE: A 30 year old male patient presented with unilateral axial proptosis left eye for 6 months with eye signs of thyroid disease and history of diplopia on up gaze, increased appetite, weight loss, excessive sweating. He also gave complaints of red, gritty, photophobic and watery eyes. His visual acuity was in the right eye 20/40 improving to 20/20 and in the left eye it was 20/40 improving to 20/20. Color vision was normal. There was no RAPD present, Eye signs included Von Graffe's sign (immobility or lagging of the upper eyelid on downward rotation of the eye), Stellwag's sign (infrequent or incomplete blinking), Dalrymple sign (widened palpebral fissure), Gifford sign (Difficulty everting the upper eyelids), Pochin's sign (blinking rate is reduced), Rosenbach's sign (unusual tremor of the eyelids), Snellen's sign (Bruit heard on auscultation over the eye), Mean's sign (increased superior scleral show on upgaze), Kocher's sign (staring and frightened appearance), Mobius' sign (inability to maintain convergence of the eyes), Suker's sign (fixation becomes difficult in extreme lateral gaze). The intraocular pressure in the RE was 17 mm Hg and LE was 19 mm of Hg. There was restriction of movements in the upgaze in the left eye. There was no corneal involvement. The visual fields were normal. Serum T3, T4 were normal with elevated TSH levels, B-scan showed thickened muscle belly of inferior rectus muscle. On CT scan Proptosis of the left eye noted (the distance from the interzygomatic line to anterior aspect of globe is 28 mm), Increase in both intra and extraconal fat is noted in the left eye , Increase in the size and altered signal intensity is noted in the muscle belly of inferior rectus of left eye with sparing of the tendon. On histologic examination Fibrosis with degenerative changes in the eye muscles, Lymphocytic cell infiltration, Accumulation of mucopolysaccharides, interstitial edema with increased collagen production was seen. The patient was treated conservatively with maintenance of euthyroid

Quantification of Orbital Apex Crowding for Screening of Dysthyroid Optic Neuropathy Using Multidetector CT

DON, a serious complication of GO, is frequently difficult to diagnose clinically in its early stages because of confounding signs and symptoms of congestive orbitopathy. We evaluated the ability of square area measurements of orbital apex crowding, calculated with MDCT, to detect DON. Fifty-six patients with GO were studied prospectively with complete neuro-ophthalmologic examination and MDCT scanning. Square measurements were taken from coronal sections 12 mm, 18 mm, and 24 mm from the interzygomatic line. The ratio between the extraocular muscle area and the orbital bone area was used as a CI. Intracranial fat prolapse through the superior orbital fissure was recorded as present or absent. Severity of optic nerve crowding was also subjectively graded on coronal images. Orbits were divided into 2 groups (with or without clinical evidence of DON) and compared. Ninety-five orbits (36 with and 59 without DON) were studied. The CIs at all 3 levels and the subjective crowding score were significantly greater in orbits with DON (P < .001). No significant difference was observed regarding intracranial fat prolapse (P = .105). The area under the ROC curves was 0.91, 0.93, and 0.87 for CIs at 12, 18, and 24 mm, respectively. The best performance was at 18 mm, where a cutoff value of 57.5% corresponded to 91.7% sensitivity, 89.8% specificity, and an odds ratio of 97.2 for detecting DON. A significant correlation (P < .001) between the CIs and VF defects was observed. Orbital CIs based on area measurements were found to predict DON more reliably than subjective grading of orbital crowding or intracranial fat prolapse.

The Globe and Orbit in Laron Syndrome

Patients with LS have an inborn growth hormone resistance, resulting in failure to generate IGF-1. The purpose of this study was to evaluate the size of the eye and orbit in LS. We retrospectively reviewed the MR imaging of the brain in 9 patients with LS for the following parameters: axial diameter of the globe, interzygomatic distance, perpendicular distance from the interzygomatic line to margins of the globe, medial-to-lateral diameter of the orbit at the anterior orbital rim, distance from the anterior orbital rim to the anterior globe, maximal distance between the medial walls of the orbits, lateral orbital wall angle, lateral orbital wall length, and mediolateral thickness of the intraorbital fat in the most cranial image of the orbit. All measurements were made bilaterally. Twenty patients referred for MR imaging for unrelated reasons served as control subjects. Compared with the control group, the patients with LS had a significantly smaller maximal globe diameter and shallower but wider orbits due to a shorter lateral wall, a smaller medial distance between the orbits, and a larger angle of the orbit. The ratio between the most anterior orbital diameter and the globe was greater than that in controls. The position of the globe was more anterior in relation to the interzygomatic line. Shallow and wide orbits and small globes relative to orbital size are seen in LS and may be secondary to IGF-1 deficiency.

Normal measurement of orbital structures: Implications for the assessment of Graves’ ophthalmopathy

Compute tomography anatomy of the orbits is well described, but only a few reports are available on normal measurements of the extraocular muscles (EOM) and globe position (GP). We obtained CT images from patients who were referred to our department for CT of the paranasal sinuses using a standard protocol for evaluation of normal orbital measurements. Our study suggests that optimum results are attained with the use of a coronal scan at a window level and width setting that results in an optimum image at the maximum muscle width for assessment of EOM and an axial scan at the mid-GP for GP and interzygomatic line. Based on our normal values, a right-to-left ratio of more than 1.4 for EOM diameter or 1.2 for GP is indicative of asymmetry. An absolute diameter of EOM > 8 mm and GP < 2 mm are abnormal.

Exorbitism Correction of Faciocraniosynostoses by Monobloc Frontofacial Advancement With Distraction Osteogenesis

Monobloc frontofacial advancement with internal distraction osteogenesis is still a relatively new technique, and the literature on exorbitism correction of syndromal faciocraniosynostosis with monobloc advancement is scarce. Using a image processing software, we measured on axial computed tomographic scans the effect of monobloc advancement on the correction of exorbitism on a large series of patients (n=38) with syndromal faciocraniosynostosis who underwent surgery for correction of cranial and facial hypoplasia. A population reference of 23 patients without faciocraniosynostoses was also measured. For each orbit, globe protrusion was expressed as the ratio between the length of the globe that is above the interzygomatic line and eye size. The results indicate that monobloc has a symmetrical effect on both eyes that is correlated to the preoperative degree of exorbitism. Longitudinal data indicate that exorbitism correction changes with time. A mean preoperative globe protrusion of 0.86 dropped sharply to 0.54 at 6 months after distraction and increased to 0.61 at 16 months after distraction removal, a value that is not significantly different from the ratio of the control group (0.60). Overall, the data suggest that a certain degree of enophthalmos in the early postoperative period does not necessarily imply a sustained overcorrection.

Normative measurements of Korean orbital structures revealed by computerized tomography.

The purposes of this study were to establish criteria for the diameters of normal extraocular muscles, the width of the optic nerve, and the globe position as revealed by CT, and to investigate the effects of age and sex on these parameters in the Korean population. Diameters of extraocular muscles (medial, lateral, superior complex, and inferior rectus), distance from the interzygomatic line to the posterior margin of the globe, width of the optic nerve-sheath complex, and length of the interzygomatic line were calculated for 214 patients on axial and direct coronal CT images, and the effects of age and sex were analyzed. Normal range for the diameters as given by mean+/-2SDs of extraocular muscles were medial rectus, 2.2--5.4 mm; lateral rectus, 2.1--4.9 mm; inferior rectus, 2.5--5.7 mm; and superior complex group, 2.6--6.4 mm. The mean optic nerve-sheath complex was 4.1 mm and the values ranged from 2.9 mm to 5.3 mm. The mean length of the interzygomatic line was 103.8 mm. The normal posterior position of the globe as here designed was 11.2 mm behind the interzygomatic line (range, 6.4--15.3 mm). All parameters under study were a little larger in males than females. Statistically, however, there was no significant difference between males' and females' results, nor between the various age groups (p>0.05). Our CT results may help clinical ophthalmologists to accurately assess enlargement of the extraocular muscles and the optic nerve as well as aiding in the evaluation of exophthalmos.

Normative measurements of orbital structures using MRI.

The purpose of this work was to establish criteria for the diameters of normal extraocular muscles and superior ophthalmic vein and width of the optic nerve-sheath complex, to determine normal globe position as seen on MRI, and to investigate the effects of age and sex on these structures. Diameters of the extraocular muscles and superior ophthalmic vein, width of the optic nerve-sheath complex, and distance from the interzygomatic line to the posterior margin of the globe were calculated for 200 normal orbits of 100 patients on T1-weighted MR scans. Normal ranges for diameters of the extraocular muscles were as follows (mean +/- 2 SD): medial rectus, 3.2-4.9 mm; lateral rectus, 2.6-4.8 mm; inferior rectus, 3.7-6.0 mm; superior group, 3.1-5.6 mm; superior oblique, 2.4-4.1 mm. The normal position of the posterior pole of the globe was 8.9 mm behind the interzygomatic line (range 5.0-12.7 mm). The mean diameters of the extraocular muscles in male patients were significantly larger than those in female patients (p < 0.001). These data may be of value in quantitatively evaluating MRI of the orbit.

Normative measurements of orbital structures using CT.

The purposes of this study were to establish criteria for the diameters of normal extraocular muscles, to determine the normal position of the globe as revealed by CT, and to investigate the effects of age and sex on these structures. Diameters of extraocular muscles, distance from the interzygomatic line to the posterior margin of the globe, width of the optic nerve-sheath complex, and length of the interzygomatic line were calculated for 200 normal orbits of 100 patients on axial and direct coronal CT images. Effects of age and sex on muscle diameters and globe position were analyzed. Normal ranges for the diameters (mean +/- 2SDs) of extraocular muscles were medial rectus, 3.3-5.0 mm; lateral rectus, 1.7-4.8 mm; inferior rectus, 3.2-6.5 mm; and superior group, 3.2-6.1 mm. The normal position of the globe was 9.4 mm behind the interzygomatic line (range, 5.9-12.8 mm). The mean diameters of the extraocular muscles and the length of the interzygomatic line in male patients were significantly larger than in female patients (p < .001). Statistically significant correlation was found between age and the diameters of the inferior and lateral rectus muscles (r = .32, p = .013; and r = .23, p = .048, respectively). Our results may be important in interpreting CT scans of the orbit because, to our knowledge, no reliable normative data exist regarding these orbital structures.