Evaluation of the ultrasound biomicroscope in strabismus surgery

Purpose: This study was done to determine the ability of the ultrasound biomicroscope (UBM) to define the distance of the horizontal extraocular muscle insertions from the limbus in children undergoing strabismus surgery. Methods. A total of 51 children undergoing primary surgery on their horizontal muscles were recruited for this study. The 50 MHz UBM was used before surgery on the muscle(s) requiring an operation to define the distance of the insertion of the horizontal rectus muscle(s) from the limbus. These data were stored on a computer and masked from the surgeon who measured the actual insertion from the limbus with calipers intraoperatively. An intraclass correlation coefficient was calculated to determine the correlation of the UBM measurement with that performed during surgery. Results: Measurement of the distance of the insertions from the limbus were taken on 79 muscles of the 51 patients: 44 medial rectus (MR) and 35 lateral rectus (LR). Mean age of the patients was 6.4 +/- 3.7 years (range, 1-15). A total of 29 children (56.9%) were female. The mean distance of MR from the limbus measured surgically was 5.2 +/- 0.6 mm (range, 4-6 mm; median, 5 mm) and measured with the UBM was 5.2 +/- 0.9 mm (range, 4-7.6 mm; median, 5.3 mm). Comparable results for the LR muscles were 6.4 +/- 0.6 mm (range, 5.5-7.5 mm; median, 6.5 mm) and 6.9 +/- 0.7 mm (range, 5.9-8.4 mm; median, 6.9 mm), respectively. An intraclass correlation coefficient of 0.71 signified good agreement between the surgical and UBM measurements of the distance from the limbus of the horizontal rectus muscle insertions. Conclusion:The UBM could be used reliably as a tool before surgery to estimate the distance of the horizontal rectus muscles from the limbus in children with strabismus.