Spectral domain optical coherence tomography to assess the insertion of extraocular rectus muscles

PurposeTo determine the distance of the horizontal rectus muscle insertion to the limbus using spectral domain optical coherence tomography (SD-OCT) and to evaluate whether results are correlated with sex, age, or axial length.MethodsThe right eyes of healthy, white subjects were imaged with SD-OCT. Subjects’ sex and age were recorded, and axial length was measured using an optical biometer. The distance from the horizontal rectus insertion to the limbus was measured. The intraclass correlation coefficient (ICC) was used to assess the reproducibility of the measurements with a subset of images. A multivariate model was adjusted to analyze whether sex, age, and axial length was correlated with insertion distance.ResultsA total of 187 right eyes were included. Mean participant age was 43.7 ± 22.1 years (range, 6-85). Of the 187 patients, 129 were female; 25 were children. Mean axial length was 23.9 ± 1.6 mm (range, 20.4–29.3). Mean rectus insertion distance to the limbus was 6.47 ± 0.52 mm (range, 5.2–7.6 mm) for the lateral rectus muscle and 5.22 ± 0.51 mm (range, 4.1–6.1 mm) for the medial rectus muscle. ICC was >0.87 for intra- and interobserver reproducibility. The insertion–limbus distance was correlated with sex, being greater in males (P = 0.040 for the lateral rectus muscle; P = 0.036 for medial rectus muscle). There was no correlation between this distance and axial length or age (P > 0.156).ConclusionsIn this study cohort, the insertion distance of the horizontal rectus muscles to the limbus on SD-OCT was greater in males than females; however, age and axial length were not correlated with insertion distance.