Ocular myasthenia is a form of myasthenia gravis in which weakened eye muscles cause double vision or drooping eyelids. It accounts for approximately 50% of people with myasthenia gravis. Myasthenia gravis is an autoimmune disorder in which the body's own antibodies block the transmission of nerve impulses to muscles, causing fluctuating weakness and muscles that tire easily. Approximately half of people who have ocular myasthenia will go on to develop generalised myasthenia gravis and weakness affecting other muscles. For the majority of people this will be within the first two years of developing ocular symptoms.
The aims of treatment for ocular myasthenia are to return the person to a state of clear vision and to prevent the development, or limit the severity of generalised myasthenia gravis. Treatments proposed for ocular myasthenia include drugs that suppress the immune system including corticosteroids and azathioprine, thymectomy (surgical removal of the thymus gland), and acetylcholinesterase inhibitors (which increases acetylcholine to compensate for the lack of acetylcholine receptors).
Two randomised controlled trials relevant to the treatment of ocular myasthenia were identified in the original version of this review and no new trials in this update. One included 43 ocular myasthenia participants treated with corticotropin (a type of corticosteroid) or placebo. The other only included three participants with ocular myasthenia and seven with generalised myasthenia gravis who were treated with intranasal neostigmine (an acetylcholinesterase inhibitor) or placebo. Neither trial enabled us to draw firm conclusions regarding how effective these treatments were in preventing progression to the development of generalised myasthenia gravis or in improving ocular symptoms. Several reasonably good quality non-randomised studies favor the use of corticosteroids and azathioprine but these and other agents need to be tested in well-designed randomised controlled trials.