Progressive External Ophthalmoplegia

Progressive external ophthalmoplegia (PEO) is characterized by slowly progressive, symmetrical immobility of the eyes which are fixed to reflex stimulation. There is no pain and the pupils are spared. The lids are typically ptotic and the orbicularis oculi weak. Unlike dysthyroid restrictive myopathy, there is no lid retraction, proptosis or congestion. However, in long standing PEO, fibrotic changes in extraocular muscles produce mechanical resistance to forced duction testing. Chronic or 'fixed' ocular myasthenia may be confused with PEO since both disorders tend to demonstrate symmnetrical total or subtotal external phthalmoplegia, ptosis, and normal pupils. Myasthenia may be resistant to Tensilon but electrophysiological testing should readily distinguish between chronic myasthenia and PEO.