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Clinical pathophysiology of thyroid eye disease: The Cone Model.

ABSTRACT: The clinical features of thyroid eye disease are dictated by the orbit's compartmentalisation; particularly, the muscle cone, which is delimited by the rectus muscles, their inter-muscular septa and the posterior sclera. The cone is anchored to the orbit apex and contains the posterior globe, the muscle bellies, a fat pad, and the blood circulation, optic nerve, and CSF sheath. It is surrounded by mobile extraconal fat, retained by the orbital septum.Thyroid eye disease is caused by expansion of muscle bellies and fat within the cone. Mechanical properties of the cone determine that the disease partitions into three phases: circumferential expansion, with forward displacement of extraconal fat; axial elongation, with increasing cone pressure; impedance of posterior venous outflow, with cone oedema and venous flow reversal.Venous flow reversal can be observed in the conjunctival circulation. It is initially transient, accompanying rises in cone pressure caused by eye movements, but later becomes permanent. It is a useful clinical sign that locates diseased muscles and anticipates venous compressive crises.Strabismus arises when inflamed rectus muscles, swollen by hydrated glycosaminoglycans, lose contractility and compliance. The incomitance is moderated by increasing stiffness affecting all the rectus muscles, as they are stretched during cone expansion.Immunomodulation, which rapidly reduces cone volume, relieving muscle elongation and stiffness, may paradoxically unmask strabismus. However, ciclosporin A suppresses late post-inflammatory fibrosis and only 4 of 71 patients so-treated required strabismus surgery.The cone model also accounts for the variety of clinical presentations of thyroid eye disease.

SUBMITTER: Meyer P

PROVIDER: S-EPMC6367424 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Clinical pathophysiology of thyroid eye disease: The Cone Model.

Meyer Paul P Das Tilak T Ghadiri Nima N Murthy Rachna R Theodoropoulou Sofia S

Eye (London, England) 20190118 2

The clinical features of thyroid eye disease are dictated by the orbit's compartmentalisation; particularly, the muscle cone, which is delimited by the rectus muscles, their inter-muscular septa and the posterior sclera. The cone is anchored to the orbit apex and contains the posterior globe, the muscle bellies, a fat pad, and the blood circulation, optic nerve, and CSF sheath. It is surrounded by mobile extraconal fat, retained by the orbital septum.Thyroid eye disease is caused by expansion of ...[more]

PMID: 30659242

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Project description:BackgroundThyroid eye disease (TED) is an autoimmune disorder that constitutes a major clinical and therapeutic challenge. Current treatment options for moderate-to-severe TED include immunotherapy, orbital radiotherapy and decompression surgery. Limited drugs of proven efficacy are available for the treatment of people with TED. Given the role in the pathogenesis of TED of interleukin (IL)-6 expression in adipocytes, fibroblasts and macrophages, the proposed theory is that inhibition of IL-6 by tocilizumab may be an effective treatment in TED by directly reducing the inflammatory response. In addition, there is an unmet need for a new treatment that can modify the natural course of the disease and reduce the incidence of late complications that can occur as a result of fibrosis following inflammation.ObjectivesTo investigate the efficacy and harms of tocilizumab for the treatment of people with TED.Search methodsWe searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2018, Issue 6); MEDLINE Ovid; Embase Ovid; LILACS BIREME; OpenGrey; the ISRCTN registry; ClinicalTrials.gov; the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) and the EU Clinical Trials Register. The date of the search was 31 July 2018.Selection criteriaWe searched for trials of tocilizumab administered by intravenous infusion using any dosage regimen, compared with placebo or intravenous glucocorticoid therapy for people with TED.Data collection and analysisWe planned to use standard methods recommended by Cochrane. The primary outcome was change in TED score (as defined by investigators). Secondary outcomes included measurement of the following parameters: change in proptosis, change in extraocular motility, change in palpebral aperture measurements, number of relapses, development of optic neuropathy and change in quality of life score. We planned to measure these outcomes at three months (range two to six months) and 12 months (range six to 18 months) post-treatment. Adverse outcomes included any adverse effects identified in the trials at any time point.Main resultsNo studies met the inclusion criteria of this review. We found one randomised, placebo-controlled, double masked study (NCT01297699). This study plans to evaluate the efficacy and harms of tocilizumab administration in people with moderate-to-severe or sight-threatening graves' ophthalmopathy (GO), that had not responded adequately to treatment with intravenous corticosteroid pulses. It was completed in December 2015 and will be assessed for inclusion in the review when data become available.Authors' conclusionsThere is currently no evidence from randomised controlled trials evaluating the efficacy and harms of tocilizumab for the treatment of people with TED.

Project description:ObjectiveTo determine the impact of thyroid eye disease (TED) on patients in various stages of the disease.BackgroundTED is a debilitating and potentially sight-threatening inflammatory autoimmune disease that is frequently misdiagnosed. Challenging quality-of-life (QoL) issues can persist long after the active phase of disease has subsided.MethodsA 62-question survey was designed as a hypothesis-generating instrument to identify key issues confronting patients ≥18 years old with physician-diagnosed TED. Questions focused primarily on physical and emotional status, and QoL experiences in the 2 months prior to the survey. Data for individual questions are presented as summary statistics. Correlations between questions were determined using χ2 analyses.ResultsThe 443 respondents were 18 to >80 years old; >90% female, and >80% from the United States. Time since TED diagnosis ranged from <1 year to >10 years. Participants provided >500 free-form responses describing experiences of living with TED. Physical signs/symptoms were experienced by 307/443 (69%) patients. Of those responding to the QoL questions (N = 394), 53 (13%) reported symptoms improving, 73 (19%) reported symptoms worsening, and 255 (65%) reported no change in the 2 months prior to the survey. The most bothersome signs/symptoms were dry/gritty eyes, light sensitivity, bulging eyes, and pressure or pain behind the eyes. Respondents <60 years were significantly (p < 0.0001) more likely to report symptomatic TED than older patients. Of 394 respondents, 179 (45%) reported feeling depressed and/or anxious, 174 (44%) reported concern about their appearance, and 73 (19%) avoided public situations; 192 (49%) reported declines in confidence or feelings of general well-being, and 78 (20%) reported an inability to achieve goals. Activities limited by TED included reading, driving, and socializing. The proportion of respondents experiencing these negative QoL measures was higher when patients reported experiencing >5 symptoms, had been diagnosed within the last 5 years, or were <60 years of age.ConclusionsPhysical manifestations of TED impact QoL for patients through all phases of the disease. It is essential that physicians and healthcare professionals become more familiar with patient experiences such as those described here to better help patients manage their disease.

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Clinical pathophysiology of thyroid eye disease: The Cone Model.

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Clinical pathophysiology of thyroid eye disease: The Cone Model.

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