Position and Circumference of the Inferior Oblique Muscle in Patients with Inferior Oblique Overaction

To determine the anatomical location of the inferior oblique (IO) muscle and any possible correlation between IO overaction and IO muscle mass. In this interventional case series, eyes undergoing primary surgery for IO overaction underwent measurement of the distance between IO muscle borders from the limbus as well as muscle belly circumference, intraoperatively. Overall, 78 eyes of 51 patients with mean age of 18.3±12.3 (range 1-48) years were evaluated. Mean distance between the anterior and posterior borders of the IO from limbus were 16.3±1.8 and 20.7±1.9 mm, respectively. Average muscle circumference was 10.7±0.9 (range 9-13) mm. There was no significant correlation between IO overaction and muscle belly circumference. Although knowledge about the anatomical location and muscle belly circumference of the IO muscle is important during surgery, there is no correlation between IO overaction and IO muscle mass.