title: Usefulness of the ratio of orbital fat to total orbit area in mild-to-moderate thyroid-associated ophthalmopathy.
abstract: OBJECTIVE
  To identify a useful predictor of thyroid-associated ophthalmopathy (TAO) from orbital CT images; to evaluate the orbital fat and extraocular muscle area ratio as a CT-derived measure; and to investigate the correlations between this ratio and the clinical manifestations in mild-to-moderate TAO.
  
  
  METHODS
  Between January 2012 and March 2013, 44 patients with TAO and 23 controls were studied prospectively. All of the patients underwent ophthalmic examinations, including clinical activity score, exophthalmometry, clinical photographs, alternate prism and cover test, duction and version test, Hess screen test, binocular single vision test, thyroid function tests and orbital CT. The cross-sectional areas of the four rectus muscles, superior oblique muscle, optic nerve and total orbit area were calculated in the coronal view 6 mm posterior from the posterior pole of globe.
  
  
  RESULTS
  The cross-sectional area measured on orbital CT showed increased orbital fat in patients with TAO and an increased orbital fat to total orbit area ratio (fat/orbit) in TAO with retraction and proptosis. There were significant correlations between fat/orbit and margin reflex distance 1 (p = 0.022), margin reflex distance 2 (p = 0.013) and the exophthalmometric value (p = 0.007).
  
  
  CONCLUSIONS
  The orbital fat to total orbit area ratio (fat/orbit) is a useful diagnostic index in mild-to-moderate TAO.
  
  
  CONCLUSIONS
  The orbital CT offers a useful diagnostic index in TAO.
authors.affiliation: 1 Department of Ophthalmology, Bundang CHA Medical Center, CHA University, Seongnam, Republic of Korea.
authors.forename: H C
authors.initials: HC
authors.lastname: Kim
authors.affiliation: 2 Department of Radiology, Bundang CHA Medical Center, CHA University, Seongnam, Republic of Korea.
authors.forename: S W
authors.initials: SW
authors.lastname: Yoon
authors.affiliation: 1 Department of Ophthalmology, Bundang CHA Medical Center, CHA University, Seongnam, Republic of Korea.
authors.forename: H
authors.initials: H
authors.lastname: Lew
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D000328:Adult; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D049970:Graves Ophthalmopathy / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009915:Orbit / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*