ocular myasthenia
Ocular myasthenia is myasthenia gravis whose signs are confined to the eyes, chiefly ptosis and diplopia. Myasthenia gravis is an autoimmune disease in which antibodies damage and destroy acetylcholine receptors in striated muscle, and the failing neuromuscular conduction causes weakness and fatigability.1 About 15% of patients with myasthenia gravis have only ocular signs, and ocular involvement is the presenting feature in 60%.1,2
The ptosis is insidious, bilateral and often asymmetric. Ptosis is typically worse at the end of the day and worsens with fatigue during 60 seconds of sustained upgaze.1 In Cogan twitch sign, the upper eyelid briefly overshoots as the eyes saccade from downgaze back to primary position.1 The diplopia is often vertical, although any extraocular muscle may be affected. Ocular myasthenia can mimic a pupil-sparing third nerve palsy or an internuclear ophthalmoplegia, but the pupils are normal.1,2
The ice pack test looks for improvement after 2 minutes of cold on the ptotic lid, and it is about 75% sensitive and highly specific.1 Acetylcholine receptor antibodies appear in only 50% to 70% of patients with ocular myasthenia, against about 90% of systemic cases.1 Of patients with only ocular signs at onset, 50% to 80% develop generalized disease, almost always within 2 years.2
More detail
Cold improves the ptosis because it inhibits the breakdown of acetylcholine by acetylcholinesterase. The edrophonium (Tensilon) test has an estimated sensitivity of 85% in ocular myasthenia. Rare deaths have occurred, so the test may be limited to cases in which less invasive tests are equivocal.1 Thoracic imaging looks for a thymoma, present in 15% of patients. Thyroid function is also tested, because autoimmune thyroid disease can be associated.1
Pyridostigmine, an anticholinesterase, may be used alone in mild disease but is usually combined with steroids and other immunosuppressants. Thymectomy is performed if a thymoma is present.1 Patients with stable deviations may benefit from muscle surgery, botulinum toxin injection, or both.1 Of patients with only ocular signs at onset, 10% to 20% remit spontaneously. Most patients who still have only ocular signs 2 years after presentation never develop generalized disease, and patients over 50 years of age are more likely to progress.2
Sources (8)
- Kanski's Clinical Ophthalmology (2024), ch. 19
- Yanoff and Duker, Ophthalmology (2023), ch. 9.17
- Benatar, M. 2006. A systematic review of diagnostic studies in myasthenia gravis. Neuromuscular Disorders, 16(7), pp.459-467.
- Grob, D., Brunner, N., Namba, T. and Pagala, M. 2008. Lifetime course of myasthenia gravis. Muscle & Nerve, 37(2), pp.141-149.
- Kerty, E., Elsais, A., Argov, Z., Evoli, A. and Gilhus, N.E. 2014. EFNS/ENS Guidelines for the treatment of ocular myasthenia. European Journal of Neurology, 21(5), pp.687-693.
- Nair, A.G., Patil-Chhablani, P., Venkatramani, D.V. and Gandhi, R.A. 2014. Ocular myasthenia gravis: A review. Indian Journal of Ophthalmology, 62(10), pp.985-991.
- Rutstein, R. and Daum, K. 1997. Anomalies of Binocular Vision: Diagnosis & Management. St. Louis: Mosby.
- Silvestri, N.J. and Wolfe, G.I. 2012. Myasthenia gravis. Seminars in Neurology, 32(3), pp.215-226.
Reviewed October 2026