title: Sensitivity of the three-step test in diagnosis of superior oblique palsy.
abstract: OBJECTIVE
  Although the Parks-Bielschowsky three-step test is the cornerstone of cyclovertical strabismus diagnosis, it has not been validated against an external benchmark. We evaluated the test's sensitivity in clinical diagnosis of superior oblique palsy in patients with unequivocal magnetic resonance imaging (MRI) evidence of superior oblique atrophy.
  
  
  METHODS
  A total of 73 strabismic patients were selected from a prospective MRI study because they exhibited superior oblique atrophy indicative of superior oblique denervation and thus confirmatory of superior oblique palsy. Of these, 50 patients who had no confounding factors were included for detailed study. Ocular motility data were evaluated to determine sensitivity of single and combined clinical findings in diagnosis of superior oblique palsy.
  
  
  RESULTS
  Maximum mean ipsilesional superior oblique cross section was reduced to 9.6 ± 0.6 mm(2) (mean ± standard error) in superior oblique palsy, representing 52% of the 18.5 ± 0.6 mm(2) contralesional superior oblique maximum cross section and 52% of the 18.4 ± 0.4 mm(2) control maximum superior oblique cross section (P < 0.001). Of the 50 patients, 35 (70%) with superior oblique atrophy fulfilled the entire three-step test. In 14 (28%) patients two steps were fulfilled; in 1 patient (2%), only one step. Affected superior oblique cross section was similar in orbits that fulfilled the three-step test (9.8 ± 0.9 mm(2)) and those that did not (9.1 ± 0.7 mm(2); P = 0.58).
  
  
  CONCLUSIONS
  The complete three-step test fails to detect 30% of cases of superior oblique atrophy. Often only two of three steps are positive in superior oblique palsy.
authors.affiliation: Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles.
authors.forename: Ajay M
authors.initials: AM
authors.lastname: Manchandia
authors.affiliation: Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles; Department of Neurology, Neuroscience Interdepartmental Program, Bioengineering Interdepartmental Program, University of California, Los Angeles. Electronic address: jld@ucla.edu.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Demer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001284:Atrophy; D002648:Child; D002675:Child, Preschool; D003941:Diagnostic Techniques, Ophthalmological; D005133:Eye Movements; D005260:Female; D006257:Head; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000473:pathology*; D011187:Posture; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013285:Strabismus / Q000175:diagnosis*; D020432:Trochlear Nerve Diseases / Q000175:diagnosis*