Orbital myositis (OM) is commonly an unilateral affliction. This paper reports a case of bilateral OM in a 45-year-old woman who presented with diplopia and acute bilateral orbital pain exacerbated by eye movement. General and neurological examinations were otherwise normal. Serum creatine kinase and thyroid function were normal. A CT scan showed bilateral enlargement of both rectus medialis and lateralis muscles. Improvement occurred after a few days of treatment with oral corticosteroids.

Ninety to ninety five percent of OM is unilateral. Bilateral cases require a search for specific aetiologies, especially thyroid ophthalmopathy. Treatment is controversial but corticosteroids are still the most common first choice drug and the outcome is generally good.

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