Myasthenia gravis (MG) is a disorder characterized by weakness of the muscles under your voluntary control. MG is caused by a communication breakdown between your nerves and muscles due to an autoimmune condition that has damaged receptors on your muscles. Your autoimmune system is producing antibodies that are adhering to these receptors, blocking chemicals that normally travel from your nerve endings to the receptors.

MG most often affects the muscles of the face, eyes, arms, and legs, as well as the muscles used for chewing, swallowing, and talking. The muscles that control breathing and swallowing can sometimes be involved as well. These are some of the signs of myasthenia gravis:

• drooping eyelids;
• double vision;
• weakness in the arms or legs; and
• difficulty breathing, talking, chewing, or swallowing.

MG can be made worse by fatigue, stress, illness, and by certain medications. Check with your doctor before taking any new prescription or over-the-counter medications. Extreme difficulty with breathing or swallowing requires emergency care.

Your ophthalmologist (Eye M.D.) can test for MG using a number of methods, including:

• blood testing, to look for abnormal antibodies;
• neurological examination of your physical condition and mental skills;
• nerve conduction testing and single-fiber electromyography,which test the electrical activity in your muscles; and
• edrophonium injection testing, to look for immediate,temporary improvement in your muscle strength.