title: Ability of an upright-supine test to differentiate skew deviation from other vertical strabismus causes.
abstract: OBJECTIVE
  To determine the sensitivity and specificity of a new upright-supine test to differentiate skew deviation from trochlear nerve palsy and other causes of vertical strabismus in a large number of patients.
  
  
  METHODS
  The study consisted of 125 consecutive patients who sought treatment from January 1, 2008, through December 31, 2010, for vertical strabismus of various causes: skew deviation (25 patients), trochlear nerve palsy (58 patients), restrictive causes (14 patients), and other causes (eg, myasthenia gravis and childhood strabismus) (28 patients). Twenty healthy participants served as controls. The deviation was measured by the prism and alternate cover test using a near target at &frac13; m in both the upright and supine positions. A vertical strabismus that decreased by 50% or more from the upright to supine position constituted a positive test result.
  
  
  RESULTS
  The upright-supine test result was positive in 20 of 25 patients with skew deviation (sensitivity, 80%) but negative in all patients with trochlear nerve palsy, restrictive, or other causes (specificity, 100%).
  
  
  CONCLUSIONS
  The upright-supine test is highly specific for differentiating skew deviation from other causes of vertical strabismus. This test could be added as a fourth step after the 3-step test, and if the result is positive, neuroimaging should be considered if indicated clinically.
authors.affiliation: Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, 555 University Ave, Toronto, Ontario M5G 1X8, Canada. agnes.wong@utoronto.ca
authors.forename: Agnes M F
authors.initials: AM
authors.lastname: Wong
authors.forename: Linda
authors.initials: L
authors.lastname: Colpa
authors.forename: Manokaraananthan
authors.initials: M
authors.lastname: Chandrakumar
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015835:Ocular Motility Disorders / Q000175:diagnosis* / Q000209:etiology; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013285:Strabismus / Q000175:diagnosis / Q000209:etiology; D016683:Supine Position; D020432:Trochlear Nerve Diseases / Q000175:diagnosis* / Q000209:etiology; D055815:Young Adult