Comparison of the swept-source anterior segment optical coherence tomography and wide-field ultrasound biomicroscopy for imaging previously operated horizontal extraocular muscles

Abstract

To assess the feasibility and accuracy of determining extraocular muscle insertion distance from the limbus of previously operated extraocular muscles with the swept-source anterior segment optical coherence tomography (AS-OCT) compared with wide-field ultrasound biomicroscope (UBM). Patients with a history of previous strabismus surgery for whom additional strabismus surgery was planned were enrolled. The insertion distance was measured by AS-OCT and UBM before reoperation and compared to the caliper measurement at the time of surgery. Observers taking measurements were masked to patient data. Patient comfort for both machines was graded on a scale of 1-10 and timing of both imaging procedures was recorded. Thirteen previously operated muscles of 6 subjects (age 20.3±4.4years; range, 11-25) were imaged. The muscle insertion could be identified in 12 cases on AS-OCT and 10 cases on UBM. The difference between the imaging result and the caliper reading was ≤1mm in 9 cases on AS-OCT and 5 cases on the UBM (69% vs 38%; P=0.03). The maximum insertion distance on AS-OCT was 13.8mm; on UBM, 10.4mm. AS-OCT had a higher grade than UBM for patient comfort (P=0.0005) and speed (P=0.001). In our cohort, AS-OCT identified the muscle insertion distance more accurately than UBM. AS-OCT measurements were judged more comfortable to the patient, and images were acquired faster. In large recessions, wide-field UBM yields suboptimal results compared with AS-OCT.