Normal Measurements of Extraocular Muscle Using Computed Tomography
Sukalaya Lerdlum MD, MSc*, Piyaporn Boonsirikamchai MD*, Ekapol Setsakol MD*
Affiliation : * Department of Radiology, Faculty of Medicine, Chulalongkorn University
Objective : Establish criteria for the diameters of normal extraocular muscles using computerized tomography
in a Thai population.
Materials and Methods : Diameters of extraocular muscles (medial, lateral, superior complex, and inferior
rectus) were calculated for 200 patients on coronal direction of screening paranasal sinuses. The effects of
age and sex were also analyzed
Result: Normal ranges for the diameters (mean + 2 SDs) of extraocular muscles were 3.7 + 0.9 mm for medial
rectus, 3.6 + 1.2 mm for lateral rectus, 4.0 + 1.4 mm for inferior rectus and 3.8 + 1.4 mm for the superior group.
The mean diameter of the extraocular muscles in male patients was not significantly larger than in female
patients (p > 0.05). There was also no statistically significant correlation between age, diameter of each
extramuscular muscle and the sum of all four muscles.
Conclusion : The present result may help radiologists and ophthalmologists to accurately assess enlargement
of the extraocular muscles, particularly in Oriental populations.
Keywords : Extraocular muscle, Normal measurement, Computed tomography
