Accuracy of Optical Coherence Tomography Measurements of Rectus Muscle Insertions in Adult Patients Undergoing Strabismus Surgery

Abstract

To assess the accuracy of anterior segment optical coherence tomography (AS-OCT) in measuring the distance of extraocular muscle (EOM) insertion to the limbus to improve preoperative assessment of adult patients undergoing strabismus surgery. Reliability analysis. setting: An institutional practice. Seventy-four adult patients scheduled for strabismus surgery on rectus muscles. The distance between the EOM insertion and the limbus was measured preoperatively with AS-OCT. The value was compared with the intraoperative measurement obtained with calipers. Additional measurements included the limbus-anterior chamber angle distance with AS-OCT and the axial length with IOLMaster. Agreement between preoperative AS-OCT and intraoperative measurements. A difference of ≤1mm was "clinically acceptable." A total of 144 muscles were analyzed. Thirty-one of 33 reoperated muscles were successfully imaged. AS-OCT measurements were within 1mm of intraoperative measurements in 77% of all muscles. The accuracy was higher for muscles with no prior surgery (83%), as compared with reoperated muscles (58%). Although the accuracy decreased when comparing reoperations to primary surgeries for the medial (79% to 63%; P= .09; 95% confidence interval [CI],-1.38 to 0.11) and the lateral rectus (81% to 49%; P= .11; 95% CI,-2.06 to 0.22), the difference was not significant. No correlation between limbus-anterior chamber angle distance and axial length was established. AS-OCT is valuable in identifying EOM insertions in primary strabismus surgeries, but the accuracy decreases in reoperations.