Evaluation of Extraocular Muscle Enlargement in Dysthyroid Ophthalmopathy

Purpose: To evaluate extraocular muscle enlargement (EME) in dysthyroid ophthalmopathy. Methods: EME was assessed by orbital computed tomography (CT) in 573 patients with dysthyroid ophthalmopathy in order to investigate the frequency and exact location of EME and the clinical features of related ocular symptoms in patients with dysthyroid ophthalmopathy. Results: Of the 573 patients examined, 187 patients (38%) showed evidence of EME on CT images. This disorder was more frequent in male patients than in female patients. EME was also more frequently seen in older patients than in younger patients. Enlargement of a single muscle was found in 55% of the 187 patients, with the most frequently affected muscle being the inferior rectus muscle. When multiple muscles were enlarged, the inferior rectus muscle was the most frequently affected, followed by the medial rectus muscle. Conclusions: Of the clinical findings specific to dysthyroid ophthalmopathy examined in the present study, the incidence of exophthalmos, upper lid swelling, superior limbic keratoconjunctivitis, keratitis, diplopia, and dysthyroid optic neuropathy was significantly increased in patients with dysthyroid ophthalmopathy, indicating a close relationship between these findings and the underlying disease, but the incidence of upper lid retraction was not significantly increased.