Morphometric study of the extraocular muscles in Thai population

Morphology of the extraocular muscles plays an important role in many ophthalmological surgeries and diagnostic imaging studies. Detailed understanding of length, width, point of insertion and the relationships between these muscles could be of significance for successful surgical outcomes. Forty-six orbital contents were extracted from formaldehyde-embalmed cadavers. Dissection was performed to reveal the extraocular muscles from their origins to insertions on the sclera. Muscle length, muscle width, distance from point of insertion to the sclerocorneal limbus, relationship between the superior oblique and superior rectus and between the inferior oblique and lateral rectus were measured. The lateral rectus and superior rectus were the longest muscles. The insertion of the medial rectus muscle was closest to the sclerocorneal limbus while the inferior rectus, lateral rectus and superior rectus insertions were progressively further apart. Only the length of the inferior rectus and medial rectus were significantly different between males and females. The distances between the superior oblique and superior rectus and between the inferior oblique and lateral rectus were slightly greater than in previous study. A direct comparison of these parameters between ethnic groups is still needed for an improvement of the procedural outcomes.