title: Effects of oblique muscle surgery on the rectus muscle pulley.
abstract: OBJECTIVE
  To determine the position of rectus muscle pulleys in Japanese eyes and to evaluate the effect of oblique muscle surgery on rectus muscle pulleys.
  
  
  METHODS
  Quasi-coronal plane MRI was used to determine area centroids of the 4 rectus muscles. The area centroids of the rectus muscles were transformed to 2-dimensional coordinates to represent pulley positions. The effects of oblique muscle surgery on the rectus muscle pulley positions in the coronal plane were evaluated in 10 subjects with cyclovertical strabismus and, as a control, pulley locations in 7 normal Japanese subjects were calculated.
  
  
  RESULTS
  The mean positions of the rectus muscle pulleys in the coronal plane did not significantly differ from previous reports on normal populations, including Caucasians. There were significant positional shifts of the individual horizontal and vertical rectus muscle pulleys in 3 (100%) patients with inferior oblique advancement, but not in eyes with inferior oblique recession and superior oblique tendon advancement surgery. The surgical cyclorotatory effect was significantly correlated with the change in the angle of inclination formed by the line connecting the vertical rectus muscles (p = 0.0234), but weakly correlated with that of the horizontal rectus muscles.
  
  
  CONCLUSIONS
  The most important factor that affects the pulley position is the amount of ocular torsion, not the difference in surgical procedure induced by oblique muscle surgery.
authors.affiliation: Department of Ophthalmology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-Ku, Okayama, Okayama, 700-8558, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Okanobu
authors.affiliation: Department of Ophthalmology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-Ku, Okayama, Okayama, 700-8558, Japan. rkono@md.okayama-u.ac.jp.
authors.forename: Reika
authors.initials: R
authors.lastname: Kono
authors.affiliation: Department of Ophthalmology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-Ku, Okayama, Okayama, 700-8558, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ohtsuki
mesh_terms: D000328:Adult; D005133:Eye Movements; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D009801:Oculomotor Muscles / Q000503:physiopathology* / Q000601:surgery*; D013285:Strabismus / Q000503:physiopathology / Q000601:surgery*; D015348:Vision, Binocular; D055815:Young Adult