Purpose: Orbital radiotherapy is recognised to be effective in the treatment of acute Graves' disease. The effect on the oculomotor muscles is still controversial.
Material and methods: To assess this effect, we conducted a prospective study on 15 patients with acute Graves' ophthalmopathy. Patients were investigated before radiotherapy, 3 months later and at long term (mean = 2 years). To study the extent of the ophthalmopathy we chose the following criteria: class IV in the NOSPECS classification system, amplitude of gaze, measurement of the thickness of oculomotor muscles (CT-scan).
Results: Improvement of the amplitude of gaze and reduction of the thickness of oculomotor muscles were not statistically significant. The oculomotor disorder was unchanged 3 months after radiotherapy. After a long term follow up (mean: 2 years), only 5 patients, among those who complained of diplopia before radiotherapy, had to be operated, especially large deviations.
Conclusion: Orbital radiotherapy does not appear as a direct treatment for oculomotor disorder in active thyroid related ophthalmopathy, however favorable indirect effects may be effective due to reduction of inflammation. As it is a harmless treatment, orbital radiotherapy may be proposed as primary treatment in active thyroid related ophthalmopathy.