Ocular myasthenia gravis
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Ocular myasthenia gravis is a form of the chronic autoimmune disorder myasthenia gravis (MG) in which the muscles responsible for controlling eye and eyelid movements are primarily affected.
The hallmark sign of MG, as a neuromuscular disorder, is muscle weakness. Often, people with the disorder first notice weakness in the muscles that control the movement of their eyes and eyelids. Later on, patients may develop muscle weakness in other areas, such as in their limbs, jaw, and throat, as well as in the muscles involved in breathing.
Basic functions that many take for granted — like chewing, swallowing, and walking — may become difficult to do. Managing these symptoms is challenging and patients may need to adapt to living with myasthenia gravis.
Ocular symptoms, such as drooping of the upper eyelids, known as ptosis, and double vision, called diplopia, occur in 15% to 50% of cases of people with MG. Between 20% and 60% of people with ocular symptoms may eventually develop generalized myasthenia gravis, in which muscle weakness and fatigue are not confined to the eye and eyelid muscles.
Ocular myasthenia gravis causes
Myasthenia gravis is caused by the body’s immune defenses inappropriately attacking certain protein receptors in muscles that receive nerve impulses. This attack interferes with nerve-muscle communication, causing muscle weakness.
While it is not completely understood why the eye muscles are more likely to be affected, it may have to do with the number of receptors present at the neuromuscular junction, where nerve and muscle cells communicate to coordinate voluntary movements.
Eye muscles also contract more frequently than limb or trunk muscles, so they might be more prone to fatigue. Another possibility is that eye muscles have a specific gene signature associated with the body’s immune response that may make them more sensitive to the disease’s immune attacks.
Ocular myasthenia gravis symptoms
Common ocular myasthenia gravis symptoms include:
- double vision (diplopia), when a person sees two images of a single object instead of one
- drooping in one or both eyelids (ptosis), which can make it difficult to keep the eyes fully open.
Muscle weakness from ocular MG often affects upward eye movement first, and tends to worsen with continuous use. For this reason, it typically is more severe toward the end of the day. Weak eye muscles also can lead to difficulties in focusing and seeing clearly. Symptoms may vary from mild to severe.
Can ocular myasthenia gravis cause blindness?
While ocular MG does not cause permanent blindness, it can cause visual disturbances and eye-related issues such as double vision and drooping eyelids.
Ocular myasthenia gravis diagnosis
Getting an ocular myasthenia gravis diagnosis can involve a combination of clinical evaluation, specialized tests, and a medical history assessment.
An ophthalmologist or neurologist will do a detailed physical exam, which includes checking eye and eyelid movement, muscle strength, and coordination. The clinician also will ask about symptoms such as drooping eyelids and double vision.
If a doctor suspects ocular MG, this may be checked with the Cogan’s lid twitch test, also known as CLT. The CLT requires the individual to hold a sustained downward gaze and then let the eyes return to the middle position. When the upper eyelid suddenly moves upward, it may appear to twitch for a brief moment, which gives the assessment its name.
To confirm whether these symptoms are related to MG, a doctor may do a diagnostic exam called the ice pack test. During this ocular myasthenia gravis diagnostic test, an ice pack is placed over a person’s closed eyelid for several minutes. If the eyelid is no longer droopy after the ice pack is removed, it may mean that the condition was caused by ocular MG.
The tensilon test also is used to help in the diagnosis of ocular myasthenia gravis. It involves a doctor giving an injection of a medication called edrophonium chloride, or tensilon. If the person’s eye symptoms are temporarily relieved, it could be an indicator of ocular MG.
Blood tests also may be done to check for the presence of known MG-causing autoantibodies that often are elevated in myasthenia gravis.
The single fiber electromyography, or SFEMG, is the most sensitive diagnostic test for MG. It measures the response of individual muscle fibers to stimulation.
Ocular myasthenia gravis treatment
Ocular myasthenia gravis treatment typically aims to manage and alleviate the symptoms associated with muscle weakness and eye-related issues. The specific treatment approach will vary from person to person, and is based on the severity of the symptoms.
Medications used to treat ocular MG may include cholinesterase inhibitors like Mestinon (pyridostigmine bromide), steroids like prednisone, or other immunosuppressants, which are medications that suppress the immune system.
If eyelid drooping does not go away after a few years, surgery to lift the eyelid may be suggested.
Ocular symptoms like dry eye can be treated with artificial tears, Eye patches and special prism eyeglasses may be used to address double vision.
The treatment of ocular MG should be customized to the individual. A trial-and-error approach may be needed to find the most effective strategy for symptom management and to try to prevent progression of ocular myasthenia gravis.
In general, the prognosis is good for people living with ocular myasthenia gravis whose symptoms are kept under control with treatment.
Myasthenia Gravis News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
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