title: Differentiating bilateral superior oblique paresis from sensory extorsion.
abstract: OBJECTIVE
  To determine whether patients historically diagnosed with bilateral superior oblique paresis (BSOP) categorized into (1) immediate-onset and (2) gradual-onset torsional diplopia groups are also distinguishable on the basis of patterns of subjective misalignment in various directions of gaze, consistent with the gradual-onset group being caused by sensory extorsion rather than by BSOP.
  
  
  METHODS
  The medical records of all patients diagnosed with BSOP, V-pattern esotropia, or V-pattern exotropia between 1978 and 2009 were retrospectively reviewed. Those patients with torsional diplopia were classified into immediate- or gradual-onset diplopia groups. The torsional misalignments measured by Lancaster red-green plots were compared, and the surgical outcomes were evaluated.
  
  
  RESULTS
  Of 38 patients identified, 27 had immediate-onset and 11 gradual-onset diplopia. There was a statistically significant difference in the increase in extorsion from up- to downgaze between the immediate- versus gradual-onset group (17.8° versus -1.5°, P < 0.001). Patients in the immediate-onset group fared significantly better with bilateral Harada-Ito procedures than with bilateral inferior oblique-weakening procedures (P = 0.02), whereas patients in the gradual-onset group fared equally well with either procedure (P = 0.72).
  
  
  CONCLUSIONS
  Extorsion in upgaze is largely absent in patients with immediate-onset BSOP but is present in both up- and downgaze in patients with gradual-onset sensory extorsion. Lancaster red-green testing aids in distinguishing these two groups. The bilateral Harada-Ito procedure is a better procedure for true BSOP, whereas a bilateral inferior oblique-weakening procedure may be preferred for patients with sensory extorsion.
authors.affiliation: The Krieger Children's Eye Center at The Wilmer Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Brinda
authors.initials: B
authors.lastname: Muthusamy
authors.forename: Han-Ying
authors.initials: HY
authors.lastname: Peggy Chang
authors.forename: Kristina
authors.initials: K
authors.lastname: Irsch
authors.forename: Howard S
authors.initials: HS
authors.lastname: Ying
authors.forename: Kirithika
authors.initials: K
authors.lastname: Muthusamy
authors.forename: Didar
authors.initials: D
authors.lastname: Anwar
authors.forename: David L
authors.initials: DL
authors.lastname: Guyton
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003941:Diagnostic Techniques, Ophthalmological; D004172:Diplopia / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009886:Ophthalmoplegia / Q000175:diagnosis*; D012189:Retrospective Studies; D020432:Trochlear Nerve Diseases / Q000175:diagnosis*; D055815:Young Adult