Minimization of Extraocular Muscle Damage in Thyroid Eye Disease Patients Following Surgery Based on Computerized Biomechanics

Background To evaluate the risk of general orbital decompression in patients with thyroid eye disease (TED).Methods In this study, we replicated the behavior of intraorbital tissue in patients with TED based on finite element analysis. The orbit and intraorbital tissues of TED patient who underwent orbital decompression were modeled as finite element models. The stress was examined at a specific location of the removed orbital wall of a patient with TED who had undergone orbital decompression, and its variation was investigated and analyzed as a function of the shape and dimension (to be removed).Results In orbital decompression surgery which removes the orbital wall in a rectangular shape, the stress at the orbital wall decreased as the width and depth of the removed orbital wall increased. In addition, the stress of the non-chamfered model (a form of general orbital decompression) was higher than that of the chamfered model. Especially, in the case of orbital decompression, it can be seen that the chamfered model compared to the non-chamfered model have the stress reduction rate from 11.08% to 97.88%.Conclusions It is inferred that if orbital decompression surgery considering the chamfered model is performed on an actual TED patient, it is expected that the damage to the extraocular muscle caused by the removed orbital wall will be reduced.

Morphological change of the posterior pole following the horizontal strabismus surgery with swept source optical coherence tomography

Extraocular muscle movement during strabismus surgery causes changes in eyeball shape. Because extraocular muscle insertion is in front of the equator, it is thought that changes due to strabismus surgery mainly occur in the anterior segment. However, changes in the posterior segment of eye may also occur, which may also result in changes in refractive error after strabismus surgery. Using a 3-dimensional reconstruction technique (en face imaging) of the swept source optical coherence tomography, we determined and quantitatively measured the posterior polar change. The deepest interface between Bruch’s membrane and the choroid could be identified as the deepest point of the eyeball (DPE), and the location of the DPE relative to the optic disc and the fovea was measured. After lateral rectus muscle recession, the DPE moved away from the fovea, but after medial rectus muscle recession, the DPE moved toward the fovea. The amount of DPE movement differed by age and preoperative refractive error. Our findings suggest that the positional shift of the rectus muscle in horizontal strabismus surgery causes a structural change in the posterior segment of the eye, and the postoperative refractive changes may be related to this shift.

Surgical Treatment and Muscle Protein Analysis of V-pattern Exotropia in Craniosynostosis

Purpose: The purpose of this study was to compare the differences of V-pattern exotropia in craniosynostosis and normal children.Methods: 39 children were included in this study, 19 craniosynostosis and 20 children in control group. They underwent comprehensive ocular examinations and received strabismus surgery. The extraocular muscle samples were analysed.Results: Compared with the control group, craniosynostosis group had larger deviation in primary and up gaze, larger V pattern, and more severe inferior oblique overaction. For 20-40, and 50-60 prism diopter exotropia, the lateral recession in the craniosynostosis group was larger than that in the control group, 7.13±0.44 mm vs 6.71±0.47 mm, 8.90±0.21 mm vs 7.75±0.46 mm (p=0.025, 0.000). The anterior transposition of craniosynostosis group was more anterior than that of control group, posterior 1.03±1.24 vs 2.68±0.94 mm (p=0.000). Compared with the control group, the extraocular muscle abnormality in craniosynostosis was significant, 32% vs 5% (p=0.031). There were 40 proteins in craniosynostosis group, which were different from those in control group.Conclusions: A larger V pattern and larger deviation is common in craniosynostosis children. For the same PD of deviation, it usually needs more recession in craniosynostosis because of the thinner and weaker extraocular muscles.

Correlation between Thyroid-stimulating Antibody Level Change and Extraocular Muscle Thickness Change in Thyroid Eye Disease

Purpose: To investigate the changes in extraocular muscle thicknesses by variations in the thyroid stimulating antibody (TSAb) level in patients with thyroid eye disease (TED).Methods: A total of 67 TED patients were enrolled. They were divided into two groups: an experimental group with clinically significant elevated TSAb levels (≥140 IU/L) and a control group (TSAb <140 IU/L). All of the lateral, medial, superior, and inferior rectus muscle thicknesses were measured with the aid of anterior segment optical coherence tomography (OCT). The average thicknesses for both eyes were recorded for each patient based on the values measured at the ends of the muscles (which become vertically thinner from the points of tendon attachment). We measured changes in TSAb levels and extraocular muscle thicknesses after two follow-up periods and sought correlations among these parameters.Results: At the initial visits, the inferior rectus muscle thickness was positively correlated with the TSAb level in the experimental group (p = 0.045, r = 0.478). None of the medial, superior, or lateral rectus muscle thicknesses were so correlated. On follow-up, the variation in TSAb level correlated negatively with changes in lateral rectus muscle thickness (p = 0.038, r = -0.357). The superior rectus muscle thickness tended to be negatively correlated with the TSAb level, but statistical significance was not attained (p = 0.146, r = -0.669). The thicknesses of the inferior and superior rectus muscles did not change over time.Conclusions: In TED patients, TSAb variations seem to reflect the extent of periorbital tissue edema, thus correlating negatively with especially lateral rectus muscle thickness changes.

Idiopathic Bilateral Extraocular Myositis in a Subject With Poorly Controlled Type 2 Diabetes Mellitus: Case Report

Background: Extraocular myositis is characterized by acute onset of orbital pain, extraocular muscle swelling, absence of thyroid disease, and effectiveness of steroid therapy. While oculomotor nerve paralysis is often observed in subjects with diabetes mellitus, extraocular muscle paralysis is very rare among various diabetic mononeuropathies. In addition, while most diabetic mononeuropathies are observed as sporadic and/or unilateral neuropathy, bilateral mononeuropathy is also very rare.Case presentation: A 58-year-old male visited our institution due to diplopia. He was diagnosed as type 2 diabetes mellitus about 10 years before and treated with oral diabetes agents. To examine the cause of his symptom, he was hospitalized in our institution. Slight ptosis was observed, and failure of adduction was observed in the right eye. Glycemic control was poor; HbA1c was 9.3%. Liver, renal, and thyroid function were within normal range. Immunoglobulin (Ig) G was slightly high, but IgA, IgM, and IgG4 were within normal range. Various antibodies were all negative. Angiotensin-converting enzyme level was within normal range. There were no abnormalities in brain magnetic resonance imaging (MRI). After admission, to alleviate glucose toxicity, we started insulin therapy. On day 17, adduction failure of the left eye was observed in addition to the right eye. Vertical movement was also impaired in both eyes. Slight ptosis was observed in both eyes, and the right eye was completely close. In orbital MRI, some high signal was detected in both extraocular muscles. We performed steroid pulse therapy twice. About 4 months later, ptosis and vertical and horizontal movements in both eyes were almost completely recovered. Finally, we diagnosed him as idiopathic bilateral extraocular myositis.Conclusions: We should bear in mind the possibility of idiopathic bilateral extraocular myositis especially in subjects with poor glycemic control, although its incident rate is extremely rare.