Quantitative computed tomography of Graves' ophthalmopathy. Extraocular muscle and orbital fat in development of optic neuropathy
S. E. Feldon, C. P. Lee, S. K. Muramatsu and J. M. Weiner
Quantitative assessment of computed tomographic (CT) scans was performed on
98 orbits of 49 patients with Graves' ophthalmopathy. Extraocular muscle
volume and orbital fat volume were determined, according to whether optic
neuropathy was absent, had developed during follow-up, or was present at
the time of scanning. No differences in muscle volume were found between
the group already having optic neuropathy and the group in which optic
neuropathy developed during follow-up. Both optic neuropathy groups,
however, had significant increases in extraocular muscle volume compared
with the group without optic neuropathy. The absolute amount of orbital fat
was the same for all groups, but the relative amount of orbital fat tended
to decrease as total orbital volume increased with development or presence
of optic neuropathy. This study establishes a quantitative relationship
between optic neuropathy and extraocular muscle enlargement in Graves'
ophthalmopathy. Orbital fat, however, does not play an important role in
the disease.
