Ocular Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune disorder where antibodies attack the connection between nerves and muscles, causing muscle weakness that worsens with activity and improves with rest. The eyes are affected first in over half of patients, causing droopy eyelids (ptosis) and double vision.

Understanding Myasthenia Gravis

In MG, antibodies block or destroy receptors at the neuromuscular junction—where nerves signal muscles to contract. The most common target is the acetylcholine receptor (AChR). This disrupts communication between nerves and muscles, causing weakness.

Types of Ocular Involvement

Ocular MG

• Symptoms limited to eyes (ptosis, diplopia)
• About 50% stay ocular only
• 50% progress to generalized MG within 2 years

Generalized MG with ocular involvement

• Eye symptoms plus weakness elsewhere
• May affect limbs, breathing, swallowing

Symptoms

Eye Symptoms

Ptosis (droopy eyelid)

• May affect one or both eyes
• Varies throughout the day
• Worse in evening or with fatigue
• May alternate between eyes
• Improves with rest or cold

Double vision (diplopia)

• Can mimic any nerve palsy pattern
• Varies with direction of gaze
• Fluctuates throughout day
• Worse with sustained gaze

Characteristic Features

• Fluctuation—symptoms vary hour to hour, day to day
• Fatigability—worse with prolonged use, better with rest
• Diurnal variation—often worse in evening
• Cold improves symptoms (basis of ice pack test)

Generalized Symptoms

If MG spreads beyond eyes:

• Weakness in arms and legs
• Difficulty chewing and swallowing (dysphagia)
• Slurred speech (dysarthria)
• Facial weakness
• Neck weakness
• Breathing difficulty—myasthenic crisis (emergency)

Warning Signs

Diagnosis

Clinical Features

• Ptosis and/or diplopia that fluctuate
• Weakness worsening with activity
• Improvement with rest
• Variable pattern not fitting typical nerve palsies

Bedside Tests

Ice pack test

• Apply ice to closed eyelid for 2 minutes
• Cooling improves neuromuscular transmission
• Ptosis improvement suggests MG
• Simple, non-invasive

Fatigability testing

• Sustained upgaze for 1-2 minutes
• Look for increasing ptosis
• Look for developing diplopia

Laboratory Tests

Acetylcholine receptor (AChR) antibodies

• Positive in 80-90% of generalized MG
• Positive in only 50-60% of ocular MG
• Highly specific—positive test confirms diagnosis

MuSK antibodies

• Check if AChR negative
• Different form of MG
• Different treatment implications

LRP4 antibodies

• Newer test for seronegative cases

Electrodiagnostic Tests

Single fiber EMG

• Most sensitive test
• Shows "jitter" in neuromuscular transmission
• Useful when antibodies negative

Repetitive nerve stimulation

• Shows decremental response
• Less sensitive than SFEMG

Imaging

CT chest

• Looking for thymoma (thymus gland tumor)
• Present in 10-15% of MG patients
• Thymic abnormalities common

Treatment

Symptomatic Treatment

Pyridostigmine (Mestinon)

• Improves nerve-muscle transmission
• First-line for symptom control
• Effect lasts a few hours
• Side effects: cramping, diarrhea, excess saliva

Immunosuppressive Treatment

Corticosteroids (Prednisone)

• Effective but many side effects
• May temporarily worsen symptoms when starting
• Often used as bridge to other treatments

Steroid-sparing immunosuppressants:

• Azathioprine (Imuran)
• Mycophenolate (CellCept)
• Take months to work
• Allow steroid dose reduction

Other Treatments

Thymectomy

• Surgical removal of thymus gland
• Recommended for thymoma
• May help even without thymoma
• Can lead to remission

Intravenous immunoglobulin (IVIG)

• For acute worsening
• Short-term effect

Plasmapheresis

• Removes antibodies from blood
• For acute worsening or crisis

Ocular MG Considerations

• Symptomatic treatment with pyridostigmine often helps
• Prisms for diplopia if stable
• Eyelid crutches or tape for ptosis
• Immunosuppression if severe or progressing

Living with Myasthenia Gravis

For comprehensive guidance on managing ocular myasthenia gravis—including daily coping strategies, medication tips, and warning signs of generalization—see our complete patient guide: Living with Ocular Myasthenia Gravis - Patient Guide.

Lifestyle Adjustments

• Rest when fatigued
• Plan activities for when you're strongest (often morning)
• Use ice packs for temporary symptom relief
• Wear sunglasses to reduce squinting

Medications to Avoid

Many medications can worsen MG. Always inform healthcare providers about your diagnosis. Examples of problematic drugs:

• Certain antibiotics (aminoglycosides, fluoroquinolones)
• Beta blockers
• Magnesium
• Some cardiac medications
• Certain anesthetics

Monitoring

• Regular follow-up with neurologist
• Pulmonary function testing
• Watch for signs of generalization
• Medication adjustment as needed

Prognosis

Ocular MG

• About 50% remain ocular only
• 50% progress to generalized (usually within 2 years)
• Early immunosuppression may reduce progression

With Treatment

• Most patients achieve good control
• Remission possible in some
• Quality of life usually good with appropriate treatment
• Lifetime condition requiring ongoing management

Frequently Asked Questions

Will my eye symptoms get worse or spread?

About half of patients with ocular MG stay ocular. The first 2 years are highest risk for generalization. Early treatment may reduce this risk.

Why do my symptoms change so much?

Fluctuation is the hallmark of MG. Weakness depends on how much neurotransmitter is available, which varies with activity, rest, temperature, stress, and other factors.

Is MG hereditary?

MG itself is not directly inherited, but there may be genetic susceptibility to autoimmune conditions. Tell your doctor about family history of autoimmune diseases.

Can I drive with MG?

It depends on your symptoms. If ptosis covers your pupil or diplopia is significant, driving may be unsafe. Discuss with your doctor and consider eye patching strategies.

What triggers myasthenic crisis?

Infections, surgery, stress, and certain medications can trigger crisis. Respiratory infections are common triggers. Seek care early if sick.

Does MG affect life expectancy?

With modern treatment, most people with MG have normal or near-normal life expectancy. The key is proper diagnosis, treatment, and avoiding complications.

References