Ocular myasthenia

Ocular myasthenia is the form of myasthenia gravis that is confined to the muscles of the eye. Myasthenia gravis is an autoimmune disease of the neuromuscular junction in which antibodies attack the acetylcholine receptors of voluntary muscle, causing weakness that varies and tires with use. In the ocular form the weakness shows as drooping of one or both eyelids (ptosis) and double vision (diplopia), while the pupil is always spared. About three quarters of all myasthenia gravis begins in the eye, and about four fifths of people with ocular onset go on to involve other muscles within two years; if the disease stays ocular for more than three years, the chance that it will generalise falls to about six percent. Acetylcholine receptor antibodies are found in only about half of people with the ocular form. Diagnosis rests on history and examination of the eyelids and eye movements, with edrophonium testing, single-fibre electromyography and blood tests as aids, and patients are also checked for thymoma. Mild cases may be left untreated; otherwise treatment starts with pyridostigmine and then prednisone, and ptosis and double vision can be managed with eyeglass aids, patching or prisms. Unlike generalised myasthenia gravis, the ocular form affects men and women equally. This entry records what the sources state and is not medical advice.