title: Variability of angle of deviation measurements in children with intermittent exotropia.
abstract: BACKGROUND
  A change in the angle of deviation is often used to monitor the change in severity of intermittent exotropia over time; nevertheless, thresholds for a clinically significant change in angle have not been determined. We analyzed variability associated with test-retest differences and short-term variability in the condition, to provide thresholds for assessing clinically significant, long-term change in angle of intermittent exotropia.
  
  
  METHODS
  Twenty-six children with intermittent exotropia (median age, 7; range, 1-13 years) underwent repeat prism and alternate cover test measures during 3 or 4 examinations (2 hours apart) over the course of a day; 95% repeatability coefficients were derived to determine test-retest differences at distance and near fixation.
  
  
  RESULTS
  Derived 95% repeatability coefficients at distance were 3.4(Δ) (95% CI, 0.7(Δ)-6.2(Δ)) for angles ≤20(Δ) and 7.2(Δ) (95% CI, 4.4(Δ)-9.9(Δ)) for angles >20(Δ); at near, 6.6(Δ) (95% CI, 3.7(Δ)-9.6(Δ)) for angles ≤20(Δ) and 12.8(Δ) (95% CI, 5.3(Δ)-20.3(Δ)) for angles >20(Δ).
  
  
  CONCLUSIONS
  Test-retest reliability data in this study provide thresholds to help determine clinically significant change in angle of strabismus in children with intermittent exotropia. These data should facilitate evidence-based assessment of long-term change in intermittent exotropia over time.
authors.affiliation: Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Hatt
authors.forename: David A
authors.initials: DA
authors.lastname: Leske
authors.forename: Laura
authors.initials: L
authors.lastname: Liebermann
authors.forename: Brian G
authors.initials: BG
authors.lastname: Mohney
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Holmes
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003941:Diagnostic Techniques, Ophthalmological; D005099:Exotropia / Q000175:diagnosis*; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D006801:Humans; D007223:Infant; D008297:Male; D015203:Reproducibility of Results; D012684:Sensory Thresholds; D015348:Vision, Binocular; D014792:Visual Acuity