title: Superior oblique muscle involvement in thyroid ophthalmopathy.
abstract: BACKGROUND
  Rectus muscle involvement in thyroid ophthalmopathy is well documented. The inferior rectus is the most frequently involved, followed by the medial, superior, and infrequently the lateral rectus. This study reports involvement of the superior oblique muscle as a contributory cause of restrictive strabismus in patients with thyroid ophthalmopathy.
  
  
  METHODS
  This is a retrospective review of four patients with known thyroid ophthalmopathy who presented with incomitant vertical strabismus, A-pattern, overdepression in adduction, underelevation in adduction, and incyclotorsion. All patients underwent preoperative orbital imaging. Two of the four patients had previous orbital decompressions. All patients underwent surgery on the SO muscle.
  
  
  RESULTS
  Preoperative scans showed enlargement of one or both SO muscles in all patients and intraoperative forced duction testing revealed restriction to elevation in adduction in all cases. Preoperative A-pattern ranged from to 6 to 22 prism diopters. All subjects had preoperative incyclotorsion, ranging from 2 and 14 degrees. Improvement of the versions, hypertropia, and cyclotorsion followed surgical weakening procedures on the SO muscle.
  
  
  CONCLUSIONS
  Thyroid ophthalmopathy may involve the SO muscle. Clinical manifestations include preoperative A-pattern strabismus, incyclotorsion, and restrictive limitation to elevation in adduction. Orbital imaging documents SO muscle enlargement. Awareness of SO involvement in thyroid ophthalmopathy assists the surgeon to develop a more precise surgical strategy to correct the hypotropia.
authors.affiliation: Jules Stein Eye Institute, Department of Ophthalmology, University of California-Los Angeles, 100 Stein Plaza, Los Angeles, CA 90095, USA.
authors.forename: Neepa M
authors.initials: NM
authors.lastname: Thacker
authors.forename: Federico G
authors.initials: FG
authors.lastname: Velez
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Demer
authors.forename: Arthur L
authors.initials: AL
authors.lastname: Rosenbaum
mesh_terms: D005133:Eye Movements / Q000502:physiology; D005500:Follow-Up Studies; D006111:Graves Disease / Q000150:complications* / Q000175:diagnosis; D006801:Humans; D008279:Magnetic Resonance Imaging; D009801:Oculomotor Muscles / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D013508:Ophthalmologic Surgical Procedures / Q000379:methods; D009915:Orbit / Q000473:pathology; D012029:Refraction, Ocular / Q000502:physiology; D013285:Strabismus / Q000175:diagnosis / Q000209:etiology* / Q000601:surgery; D016896:Treatment Outcome; D014792:Visual Acuity