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Christine Lynn Bokman, Shoaib Ugradar, Daniel Rootman; Measurement of Medial Wall Bowing and Clinical Associations in Thyroid Eye Disease. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5613. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To propose and validate a measure of medial wall bowing in Thyroid Eye Disease (TED) and to assess the clinical correlates of bowing in TED.
In this cross-sectional cohort study, all patients affected with TED seen by a single specialist. Eligible participants were adults with clinical evidence of TED and either computed tomography or magnetic resonance imaging of the orbits. The primary outcome measure was prevalence of medial wall bowing. Secondary outcomes included the associations between medial wall bowing and exophthalmometry, diplopia, rectus muscle restriction, dysthyroid optic neuropathy (DON) and strabismus. Medial wall bowing was defined as medial divergence of the medial wall from a straight line drawn between the anterior lacrimal crest and the middle of the optic canal and measured radiographically using axial images of the orbits (Figure 1). Volumetric analysis of bowing was performed on a sample of orbits with and without bowing. Volumetric and axial single slice measurements were compared (Figure 2). Bivariate statistics and multivariate logistical regression were performed.
The final sample included 112 orbital images from 66 patients with TED. Medial wall bowing was found to be evident in 11.6% (n=13/112) of orbits. In bivariate analysis, medial wall bowing was significantly associated with greater Hertel measurements (mean difference = 2.4mm, p<0.03), horizontal muscle restriction (mean difference = 10.8 degrees, p<0.01) and vertical muscle restriction (mean difference = 11.2 degrees, p<0.01). Patients affected by optic neuropathy (OR=19.8x, p<0.01), diplopia (Gorman score 1) (OR=8.7x, p<0.01), strabismus (OR=3.9x, p<0.03) or horizontal restriction (OR=2.2x, p<0.01) all were more likely to demonstrate medial wall bowing. In multivariate logistic regression only optic neuropathy (p=0.01) and diplopia of any type (p<0.01) maintained significant association. Analysis of the volume for medial wall bowing demonstrated that the height of the arc at the peak of bowing on an axial image of a 2D CT scan correlated highly with the total volume of bowing (r = 0.90, p<0.001).
The identification of medial wall bowing on CT or MRI is associated with clinical measures of disease severity, including diplopia and DON.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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