The use of real-time orbital ultrasound in Graves' ophthalmopathy: a comparison with computed tomography

Evaluation of the severity of orbital involvement and likelihood of the development of optic neuropathy in Graves' disease can be clinically difficult. We describe the use of real-time orbital ultrasound scanning to measure the medial rectus muscle width in 20 patients with Graves' ophthalmopathy and 21 normal individuals. The normal reference interval (to 2 SDs) was 1.75 to 4.07 mm. Significantly (p less than 0.001; Mann Whitney U-test) larger values were observed in the patients compared with controls, and there was good correlation between medial rectus width and a clinical index of disease severity in individual eyes (p less than 0.001; Spearman rank correlation coefficient). Comparison of the medial rectus measurements obtained using orbital computed tomography and ultrasound showed positive correlation at the p less than 0.001 significance level. Computed tomographic medial rectus measurements also correlated with horizontal and vertical muscle indices for that orbit. We suggest that real-time ultrasound of medial rectus width, using widely available equipment, provides an accurate, simple and non-invasive means of evaluating the orbits of patients with Graves' disease. Repeated measurements may be of value in identifying patients at high risk of visual failure, and in following prospectively the orbital response to therapy in patients with Graves' ophthalmopathy.