On the frontline: what an optometrist needs to know about myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease that affects the voluntary skeletal muscles. It is characterized by transient weakness of the muscles that improves with rest. Muscle weakness involving the eyes can produce signs or symptoms of diplopia, blurred vision, ptosis, and ophthalmoplegia. Ptosis is defined as an abnormal eyelid "drooping" beyond the normal 1 to 2 mm of the upper limbus of the cornea. Hence, most patients with MG have ophthalmic manifestations. Among all patients with MG, up to half will have exclusively ocular symptoms. In these cases, the condition is referred to as ocular myasthenia.

A 60-year-old man was referred from a neurology clinic for management of intermittent diplopia for greater than 1 year and intermittent bilateral ptosis for the prior year. He reported that he first noticed symptoms of MG at the age of 42, but did not receive the diagnosis until 1 year before his aforementioned neurology examination. He was prescribed spectacles with bilateral ptosis crutches. A diagnosis of severe seronegative MG was subsequently confirmed with neurologic examination and antibody testing.

Because patients with undiagnosed myasthenia gravis may present initially with ocular signs or symptoms, it is important for the optometrist to be familiar with the condition and the simple "in-office" tests that can be performed to establish a tentative diagnosis and management plan. The optometrist can also participate in the management of ocular manifestations of myasthenia and should be familiar with the use of a ptosis crutch (in addition to prism spectacles or occlusion therapies if indicated) as a nonsurgical intervention for ptosis.