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Localising rectus muscle insertions using high frequency wide-field ultrasound biomicroscopy
  1. Hayat Ahmad Khan,
  2. David R Smith,
  3. Stephen P Kraft
  1. Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
  1. Correspondence to Dr Stephen P Kraft, Department of Ophthalmology and Vision Sciences, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada; stephen.kraft{at}


Aim The ultrasound biomicroscope (UBM) can accurately locate an extraocular muscle (EOM) insertion. The authors compared the accuracy of the Sonomed UBM (SUBM), a new ‘wide-field ultrasound biomicroscope’, with the older model Humphrey UBM (HUBM) in localising EOM insertions and compared their ranges of detection of muscle insertions.

Methods Prospective, double-masked, observational study of 27 patients undergoing primary (n=40 muscles) or repeat (n=10 muscles) horizontal or vertical rectus muscle surgery. EOM insertional distances were measured with SUBM, and then intraoperatively with callipers. A Bland–Altman analysis and intraclass correlation coefficient were used to compare the SUBM and surgical data.

Results For all muscles, the differences between SUBM and surgery measurements were less than 1.0 mm. The mean of the SUBM insertion distances was 6.67 mm (SD 1.65 mm) versus 6.7 mm (SD 1.6 mm) at surgery. The intraclass correlation coefficient showed ‘excellent’ correlation between the two sets of data and was higher than that reported with HUBM. The image quality with the SUBM was superior to the HUBM, and its range of field was much larger (14×18 mm vs 5×6 mm).

Conclusion The SUBM with its smaller, more manoeuvrable probe handpiece and a wider scanning field was more accurate in detecting muscle insertions compared with HUBM.

  • Ocular imaging
  • extraocular muscles
  • strabismus surgery
  • strabismus treatment
  • ultrasound
  • muscles
  • imaging
  • eye (globe)
  • treatment medical
  • physiology
  • anatomy
  • treatment surgery

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  • Presented in part at the XI Meeting of the International Strabismological Association, Istanbul, Turkey, 22–25 September 2010.

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval Hospital for Sick Children's Ethics Review Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement The authors of the article agree to share the data if required at any point of time by BMJ reviewers. Data are available on request from HAK (hayatkhan123{at}