title: Quantitative assessment of inferior oblique muscle overaction using photographs of the cardinal positions of gaze.
abstract: OBJECTIVE
  To report a novel method for measuring the degree of inferior oblique muscle overaction and to investigate the correlation with other factors.
  
  
  METHODS
  Cross-sectional diagnostic study.
  
  
  METHODS
  One hundred and forty-two eyes (120 patients) were enrolled in this study. Subjects underwent a full orthoptic examination and photographs were obtained in the cardinal positions of gaze. The images were processed using Photoshop and analyzed using the ImageJ program to measure the degree of inferior oblique muscle overaction. Reproducibility or interobserver variability was assessed by Bland-Altman plots and by calculation of the intraclass correlation coefficient (ICC). The correlation between the degree of inferior oblique muscle overaction and the associated factors was estimated with linear regression analysis.
  
  
  RESULTS
  The mean angle of inferior oblique muscle overaction was 17.8 ± 10.1 degrees (range, 1.8-54.1 degrees). The 95% limit of agreement of interobserver variability for the degree of inferior oblique muscle overaction was ±1.76 degrees, and ICC was 0.98. The angle of inferior oblique muscle overaction showed significant correlation with the clinical grading scale (R = 0.549, P < .001) and with hypertropia in the adducted position (R = 0.300, P = .001). The mean angles of inferior oblique muscle overaction classified into grades 1, 2, 3, and 4 according to the clinical grading scale were 10.5 ± 9.1 degrees, 16.8 ± 7.8 degrees, 24.3 ± 8.8 degrees, and 40.0 ± 12.2 degrees, respectively (P < .001).
  
  
  CONCLUSIONS
  We describe a new method for measuring the degree of inferior oblique muscle overaction using photographs of the cardinal positions. It has the potential to be a diagnostic tool that measures inferior oblique muscle overaction with minimal observer dependency.
authors: Department of Ophthalmology, College of Medicine, Hanyang University School of Medicine, Seoul, South Korea.
authors: Han Woong
authors: HW
authors: Lim
authors: Department of Ophthalmology, College of Medicine, Hanyang University School of Medicine, Seoul, South Korea.
authors: Jung Wook
authors: JW
authors: Lee
authors: Department of Ophthalmology, College of Medicine, Hanyang University School of Medicine, Seoul, South Korea.
authors: Eunhee
authors: E
authors: Hong
authors: Department of Ophthalmology, College of Medicine, Hanyang University School of Medicine, Seoul, South Korea.
authors: Yumi
authors: Y
authors: Song
authors: Department of Ophthalmology, College of Medicine, Hanyang University School of Medicine, Seoul, South Korea.
authors: Min Ho
authors: MH
authors: Kang
authors: Department of Ophthalmology, College of Medicine, Hanyang University School of Medicine, Seoul, South Korea.
authors: Mincheol
authors: M
authors: Seong
authors: Department of Ophthalmology, College of Medicine, Hanyang University School of Medicine, Seoul, South Korea.
authors: Hee Yoon
authors: HY
authors: Cho
authors: Department of Ophthalmology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea. Electronic address: syoh@skku.edu.
authors: Sei Yeul
authors: SY
authors: Oh
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D005403:Fixation, Ocular; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015835:Ocular Motility Disorders / Q000175:diagnosis*; D009801:Oculomotor Muscles / Q000473:pathology*; D010781:Photography / Q000379:methods*; D015203:Reproducibility of Results; D013285:Strabismus / Q000175:diagnosis*; D020432:Trochlear Nerve Diseases / Q000175:diagnosis*; D015348:Vision, Binocular; D014796:Visual Perception; D055815:Young Adult