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Ocular Myasthenia Gravis: Signs, Causes & Treatment

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Ocular myasthenia gravis is a disease that causes weakness in the eye muscles. This may lead to double vision and drooping eyelids. It has the possibility of progressing into generalized myasthenia gravis, which affects muscles in the entire body.

Treatments for ocular myasthenia gravis include the use of drugs or surgery. Treatments are more effective when they are implemented earlier.

What Is Ocular Myasthenia Gravis

Ocular myasthenia gravis is an autoimmune disease that affects the ocular muscles.

Normally, acetylcholine is transmitted from the neuromuscular junction and arrives at acetylcholine receptors, which allow muscles to contract. In patients suffering from ocular myasthenia gravis, antibodies interfere with acetylcholine receptors, blocking them from receiving acetylcholine and causing difficulty with muscle contraction.

Symptom

There are two common symptoms that occur in patients suffering from ocular myasthenia gravis.

These symptoms become more severe the longer a patient goes without rest. They usually improve after resting.

Diagnosis of Ocular Myasthenia Gravis

Doctors use a variety of methods to diagnose ocular myasthenia gravis. If you have been suffering from double vision or drooping eyelids, visit a medical professional to diagnose whether you may be suffering from ocular myasthenia gravis.

These are different tests specialists may use to diagnose ocular myasthenia gravis:

  • Sleep test: The patient is examined prior to the test and must then sleep for 30 minutes. After the 30-minute period, doctors observe whether the patient’s symptoms are still present. If symptoms are not visible, and especially if they then become visible within the next 30 minutes, it may be an indication the patient is suffering from ocular myasthenia gravis.
  • Ice test: An ice pack is placed over the patient’s eyes for 2 to 5 minutes. If, after the allotted time, the patient’s eyelids droop at least 2 millimeters less than they did prior to the test, they may be suffering from ocular myasthenia gravis. Importantly, there are no objective guidelines to the interpretation of the ice test, so different doctors may come to different conclusions based on a patient’s results.
  • Antibody test: This test is conducted through a blood sample taken from the patient. Given that ocular myasthenia gravis is caused by antibodies blocking acetylcholine receptors, an overabundance of those antibodies can be found through a blood test. However, for those with only ocular symptoms of myasthenia gravis, the antibody test may not produce a conclusive answer.
  • Edrophonium test: This test works by injecting edrophonium chloride into the patient. Patients whose symptoms alleviate shortly after injection are likely suffering from ocular myasthenia gravis. However, edrophonium tests are rarely administered due to the potential for mild as well as serious side effects.
  • Neostigmine test: This test is similar to the edrophonium test, but it utilizes a drug that takes longer to act.
  • Repetitive nerve stimulation: This test involves doctors using electrical stimulation on specific nerves and studying the results. Individuals suffering from ocular myasthenia gravis may see a reduced response compared to those who don’t have the disease.
  • Electrical nerve testing: Doctors may resort to single-fiber electromyography, a test in which a needle is inserted near the patient’s eye to record electric signals caused by muscle movement. If the signals detected are different from normal, the patient may have ocular myasthenia gravis.
  • Scanning: Chest scans are recommended for those suffering from myasthenia gravis, as those with the disease may have problems with their thymus gland, or they may have developed a thymoma.

Causes

Ocular myasthenia gravis is not an inherited disease or a contagious one, meaning it cannot be spread from one person to another.

Patients may begin experiencing ocular myasthenia gravis at any age. While generalized myasthenia gravis is most commonly found in young adult women under 40 or men over 60, ocular myasthenia gravis without other affected areas is most commonly found in men over 40.

In some cases, a pregnant person suffering from myasthenia gravis may pass antibodies onto their child, resulting in neonatal myasthenia. However, symptoms can be treated, and the condition generally disappears after two to three months.

Treatments for Ocular Myasthenia Gravis

Treatments for the condition range from medications to surgery.

Acetylcholinesterase Inhibitors

Symptoms of ocular myasthenia gravis can be treated with drugs that strengthen the nerve signals to muscles. One of the commonly used acetylcholinesterase inhibitors is called pyridostigmine bromide, which is taken as a tablet multiple times a day and serves to reduce symptoms of the disease.

However, the drug presents serious side effects if used alongside different substances. Because of this, it must be used with caution.

Anti-Inflammatory Drugs

Another commonly prescribed method to treat symptoms of ocular myasthenia gravis is through the use of drugs that control antibody production. These drugs, when taken consistently over a long period of time under medical supervision, can result in decreased symptoms for most patients.

Anti-inflammatory drugs generally do not get rid of the disease on their own, but they may decrease the risk of ocular myasthenia gravis progressing into generalized myasthenia gravis.

These drugs also present the risk of serious side effects. They should only be used under instruction from a medical professional.

Thymectomy

Removal of the thymus gland through surgery can lessen symptoms of ocular myasthenia gravis in the majority of cases. In some cases, it may outright cure it.

According to recent research, patients that receive a thymectomy when they only have ocular myasthenia gravis, as opposed to generalized myasthenia gravis, may have a higher chance of remission following a thymectomy.

Plasmapheresis

During this procedure, plasma with abnormal antibodies is removed from the patient and replaced with a plasma substitute. This method does not cure the disease. It is generally only used in extreme emergency cases or as preparation for surgery such as a thymectomy.

Ocular Myasthenia Gravis vs. Generalized Myasthenia Gravis

While ocular myasthenia gravis results in symptoms such as double vision and drooping eyelids, generalized myasthenia gravis affects muscles all over the body, not just in the eyes.

Patients suffering from generalized myasthenia gravis may have trouble with any of the muscles in their body, including but not limited to the following:

  • Changes in facial expressions
  • Struggles with swallowing
  • Shortness of breath
  • Dysarthria (commonly known as slurred speech)
  • Weakness in the limbs, including the neck, arms, legs, hands, and fingers

A multitude of studies have shown that in over 50 percent of patients with ocular myasthenia gravis, the disease often progresses into generalized myasthenia gravis within the span of two years. Early diagnosis of the disease is crucial, as treatment while the disease is only ocular can decrease the chances of it progressing into generalized myasthenia gravis.

References

  1. Myasthenia Gravis Fact Sheet. (March 2020). National Institute of Neurological Disorders and Stroke.
  2. Ocular Myasthenia Gravis: A Review. (October 2014). Indian Journal of Ophthalmology.
  3. Diplopia. (February 2022). National Library of Medicine.
  4. Ptosis. (May 2022). StatPearls.
  5. Myasthenia Gravis. (February 2022). U.S. Department of Women’s Services.
  6. Diagnosis of Myasthenia Gravis. (April 2021). Journal of Clinical Medicine.
  7. Neonatal Myasthenia Gravis. (February 2022). StatPearls.
  8. Pyridostigmine Bromide. (August 2022). National Library of Medicine.
  9. Thymectomy in Ocular Myasthenia Gravis Before Generalization Results in a Higher Remission Rate. (March 2022). European Journal of Cardio-Thoracic Surgery.
  10. Outcome of Therapeutic Plasma Exchange in Myasthenia Gravis Patients. (December 2020). Journal of Family Medicine and Primary Care.

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