title: Fusion can mask the relationships between fundus torsion, oblique muscle overaction/underaction, and A- and V-pattern strabismus.
abstract: OBJECTIVE
  To evaluate relationships between fundus torsion, A- or V-pattern strabismus, and oblique muscle over- or underaction, and to explore the influence of stereopsis on these relationships.
  
  
  METHODS
  The medical records of patients with A or V patterns and/or abnormal ocular torsion seen at a single institution over nearly 30 years were retrospectively reviewed. Data collected were age, objective fundus torsion (estimated by indirect ophthalmoscopy), horizontal deviations in up- and downgaze, oblique muscle over- or underaction, and stereopsis.
  
  
  RESULTS
  A total of 396 patients were included. A patterns were observed in 121 patients (30.6%); V patterns in 90 (22.7%). Of the A-pattern patients, 73.6% had superior oblique muscle overaction, whereas 71.1% of the V-pattern patients had inferior oblique muscle overaction (P < 0.0001, r = 0.71), increasing to 78.6% and 86.3%, respectively, for patients without stereopsis (r = 0.78). Of the patients with fundus intorsion, 78.7% had superior oblique muscle overaction, whereas 74.4% of those with fundus extorsion had inferior oblique muscle overaction (P < 0.0001, r = 0.79), increasing to 83.5% and 82.8%, respectively, for patients without stereopsis (r = 0.82). Fundus intorsion occurred in 76% of the A-pattern patients, whereas fundus extorsion occurred in 71.1% of the V-pattern patients (P < 0.0001, r = 0.73), increasing to 78.6% and 86.3%, respectively, for patients without stereopsis (r = 0.79).
  
  
  CONCLUSIONS
  Strong correlations were found between fundus intorsion, superior oblique muscle overaction, and A patterns, and between fundus extorsion, inferior oblique muscle overaction, and V patterns. These correlations increased in patients without stereopsis, suggesting that the presence of binocular fusion can partially interfere with the close correlation of these parameters.
authors.affiliation: The Krieger Children's Eye Center at The Wilmer Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-9028, USA.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Deng
authors.forename: Kristina
authors.initials: K
authors.lastname: Irsch
authors.forename: Ron
authors.initials: R
authors.lastname: Gutmark
authors.forename: Pittaya
authors.initials: P
authors.lastname: Phamonvaechavan
authors.forename: Fong-Yee
authors.initials: FY
authors.lastname: Foo
authors.forename: Didar S
authors.initials: DS
authors.lastname: Anwar
authors.forename: David L
authors.initials: DL
authors.lastname: Guyton
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D005654:Fundus Oculi; D006801:Humans; D008297:Male; D009801:Oculomotor Muscles / Q000502:physiology*; D012189:Retrospective Studies; D013285:Strabismus / Q000473:pathology* / Q000503:physiopathology; D014102:Torsion Abnormality / Q000473:pathology*; D055815:Young Adult