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R. Siddiqi, A. Jacks, P.A. Good; Standardised Echography in the Diagnosis & Management of Thyroid Eye Disease . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3657.
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Purpose: The most common cause of proptos is is enlargement of the extra-ocular muscles due to Thyroid Eye Disease (TED). However, differential diagnosis can be difficult especially if the proptosis is mild. Neuro-imaging can be misleading especially in the presence of hyperdense orbital fat. Previous studies have shown that standardised echography can be useful in the diagnosis and management of TED. This study aims to examine the use of standardised A and B-scan echography in the early diagnosis of TED. Methods: Twenty patients (14 females, 6 males) with abnormal thyroid function and mild proptosis underwent standardised echography using the TED diagnostic programme on the BVI Quantel Cinescan S. Three measurements of all six muscles were made in the mid-portion of the muscle for each eye; and compared to 40 age and sex matched controls. Statistical analysis was with t test. Cohen's Kappa statistics were used to evaluate inter- and intra- observer repeatability. Results: The group mean muscle index (average of all six muscle diameters) was 5.6 mm (sd 0.7) for the group with presumed TED compared to 3.8 mm (sd 0.5) in the control group p < 0.005. Thirty out of forty eyes had a muscle index greater than laboratory normal limits of 4.5 and the remaining ten patients had one or two hypertrophied muscles (greater than 5 mm diameter) in each eye. Notably, hypertrophy of the Superior Rectus was noted in twenty-four eyes. Conclusions: This study has shown that standardised A and B scan echography provides accurate measurement of the extra-ocular muscles (EOM's) in TED, aiding in differential diagnosis and management. The muscle index as devised by Ossoinig provides an accurate quantitative evaluation of all six EOM's. The severity of TED and the possibility of compressive optic neuropathy can also be established using this method. A notable finding was the high incidence of hypertrophy of the superior rectus muscle in TED, which has not previously been reported.
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