Measurement of the Limbus-Insertion Distance in Adult Strabismus Patients with Anterior Segment Optical Coherence Tomography

PURPOSE. To determine the ability of the anterior segment optical coherence tomography (AS-OCT) in measuring the distance from the corneoscleral limbus to the insertion site of the horizontal extraocular muscles in adult patients with strabismus. METHODS. A total of 16 strabismus patients were recruited for this study. The limbus-insertion distances of the horizontal rectus muscles were measured with AS-OCT preoperatively and calipers intraoperatively. The intraclass correlation coefficient (ICC), Pearson's correlation coefficients, and Bland-Altman plots were used to evaluate the degree of agreement between the two methods of measurements. RESULTS. Measurements of the limbus-insertion distances were taken on 37 muscles of the 16 patients: 18 medial rectus (MR) and 19 lateral rectus (LR). The mean limbus-insertion distance of MR and LR measured intraoperatively were 5.32 +/- 0.44 mm (range, 4.5-6.1 mm) and 6.58 +/- 0.53 mm (range, 5.5-7.5 mm). Comparable results measured with the AS-OCT were 5.72 +/- 0.60 mm (range, 4.62-6.82 mm) and 6.80 +/- 0.61 mm (range, 5.8-7.86 mm). For MR group and LR group, the values of limbus-insertion distance showed high Pearson's correlation coefficients (0.729 and 0.786, respectively). With the ICC analysis excellent agreement was observed for the measurements of LR group (ICC = 0.75). Fair to good agreement was observed for the MR group (ICC = 0.61). Bland-Altman plots also showed good agreement between the two methods of measurements. CONCLUSIONS. AS-OCT can image the structure of horizontal rectus muscles well and provide good reliability and accuracy in measurement of the limbus-insertion distance. (Invest Ophthalmol Vis Sci. 2011;52:8370-8373) DOI: 10.1167/iovs.117752