The purpose of this study was to investigate the accuracy to locate muscle insertion positions before and after strabismus surgery using wide-field ultrasound biomicroscopy with the bag / balloon technique. Thirty-nine muscles of 22 adult patients aged 34.7 ±15.5 years were assessed; 19 medial rectus and 20 lateral rectus. There was no significant difference between ultrasound and caliper measurements for medial and lateral recti. Of 39 muscles, 27 were naïve and 12 had prior surgery. A difference was found between measurements for naïve (0.56 ±0.54mm) and reoperation muscles (0.91 ±0.81mm). Follow-up measurements for 25 muscles of 14 patients were recorded at a mean of 191.9 ±82.55 days postoperatively; 12 recessions and 13 resections. The mean difference was <1mm for 64% of muscles. The ultrasound system allowed maximum distance with sufficient quality visualisation of 14/15mm from the limbus. On average postoperative ultrasound measurements were 1.15mm greater than caliper measurements for recessed muscles. There was no significant difference of resected muscles (mean difference of -0.07mm).