The study provides quantitative data, in normal subjects of different ages, on the thickness and size of EOM and the volume of other orbital tissues by MRI, to serve as a basis for further studies on the morphological changes of EOM in various orbital diseases.

Extraocular muscle enlargement was seen in all patient groups with TAO of differing levels of severity. Measurements with MRI of muscle volume or maximal cross-sectional area are considered good indicators of muscle enlargement in TAO.

The results show that the orbital fatty tissue involvement is closely related to the degree of exophthalmos. For studying exophthalmos in TAO, the volumetric change, not only in ocular muscles, but also in orbital fatty tissue, should be taken into consideration.

MRI technique makes it possible to observe and evaluate quantitatively the volume of all six extraocular muscles and the orbital fatty tissue in dysthyroid ophthalmopathy. It also makes it possible to evaluate changes in morphology during eye muscle contraction.