title: The accuracy of anterior segment optical coherence tomography (AS-OCT) in localizing extraocular rectus muscles insertions.
abstract: OBJECTIVE
  To evaluate the accuracy of the anterior segment optical coherence tomography (AS-OCT) in measuring the distance from the limbus to the insertion of primary and previously operated rectus muscles in children.
  
  
  METHODS
  In this prospective, double masked, observational study the distance of the extraocular muscle insertion from the limbus measured by AS-OCT preoperatively was compared to intraoperative measurement using the surgical calipers. Consecutive patients 4-18 years of age undergoing primary or repeat strabismus surgery on horizontal or vertical rectus muscles between September 2013 and May 2014 were included. Patients with any condition that interfered with imaging were excluded. Participants were asked to look in the direction opposite to the muscle to ensure that the middle third of the muscle was being imaged and measured.
  
  
  RESULTS
  A total of 65 muscles were evaluated, including 9 muscles undergoing reoperation and 10 vertical rectus muscles. Of these, 62 muscles were successfully imaged. In all reoperated eyes, the AS-OCT measurements were within 1 mm of the intraoperative measurements. Overall, 89.7% (95% CI, 78.8%-96.1%) of the measurements were within the 1 mm difference considered "clinically acceptable." The intraclass correlation coefficient comparing the reliability of the AS-OCT measurements with intraoperative measurements was 0.73 (95% CI, 0.53-0.85), or "good" agreement.
  
  
  CONCLUSIONS
  AS-OCT can accurately detect rectus muscle insertions in primary or previously operated cases in children as young as 4 years of age.
authors.affiliation: Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada. Electronic address: cherylngo@gmail.com.
authors.forename: Cheryl S
authors.initials: CS
authors.lastname: Ngo
authors.affiliation: Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Smith
authors.affiliation: Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Kraft
mesh_terms: D000293:Adolescent; D000869:Anterior Eye Segment; D002648:Child; D002675:Child, Preschool; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D009801:Oculomotor Muscles / Q000473:pathology* / Q000601:surgery; D057234:Preoperative Period; D011446:Prospective Studies; D015203:Reproducibility of Results; D012590:Sclera / Q000473:pathology*; D013285:Strabismus / Q000175:diagnosis* / Q000601:surgery; D041623:Tomography, Optical Coherence / Q000592:standards*