Anterior segment optical coherence tomography of the horizontal and vertical extraocular muscles with measurement of the insertion to limbus distance

Purpose: To assess the possibility of determining the insertion distance from the limbus of horizontal and vertical extraocular rectus muscles with anterior segment optical coherence tomography (AS-OCT). Methods: The right eyes of 46 patients underwent AS-OCT. The horizontal and vertical extraocular rectus muscle insertion distances from the limbus were measured in a masked fashion by two pediatric ophthalmologists. Results: Forty-two lateral rectus, 43 medial rectus, 35 inferior rectus, and 40 superior rectus muscles of the right eyes of 46 patients were included. Insertion to limbus measurements (mean ± SD) were as follows: lateral rectus = mean 6.8 ± 0.7 mm, range = 4.8 to 8.4 mm; medial rectus = mean 5.7 ± 0.8 mm, range = 4.3 to 7.8 mm; inferior rectus = mean 6.0 ± 0.6 mm, range = 4.8 to 7.0 mm; superior rectus = mean 6.8 ± 0.6 mm, range = 5.5 to 8.1 mm. The intraobserver and interobserver correlation coefficients for the insertion to limbus measurements of all four rectus muscles exceeded 0.75 (excellent correlation). Conclusions: The study showed that AS-OCT is capable of imaging all four of the rectus muscle insertions and measuring the insertion to limbus distance, and is the second AS-OCT study to image the superior and inferior rectus muscle insertions. The insertion to limbus measurements between examiners and on repeat measurements were consistent and reproducible. The ability to accurately image extraocular rectus muscle insertions may have future implications for the preoperative procedure planning in patients who have had previous surgery.