Ocular Myasthenia Gravis

Ocular myasthenia gravis (OMG) is a form of myasthenia gravis in which muscle weakness is limited to the eye muscles. It causes drooping eyelids (ptosis) and double vision without affecting other muscles in the body.

Understanding Ocular Myasthenia

Myasthenia gravis is an autoimmune disease where antibodies attack the neuromuscular junction—where nerves connect to muscles. In ocular myasthenia, this attack affects only the muscles that move the eyes and eyelids.

The eye muscles may be particularly vulnerable because:

• They contract rapidly and frequently
• They have fewer acetylcholine receptors per junction
• They lack the ability to increase receptor density

Symptoms

Ptosis (Drooping Eyelid)

• One or both eyelids
• Often asymmetric
• Worse later in day or with fatigue
• May shift from one eye to other
• Improves with rest or sleep

Diplopia (Double Vision)

• Variable pattern
• May mimic any cranial nerve palsy
• Often inconsistent day to day
• Worse with sustained gaze
• Improves with rest

Fatigue Pattern

• Morning: Symptoms better after sleep
• Evening: Symptoms worse after use
• Fatigability: Worsens with sustained activity

Diagnosis

Clinical Examination

• Sustained upgaze test (fatigable ptosis)
• Checking for Cogan's lid twitch
• Ice pack test—improvement with cooling
• See Ice Test

Antibody Testing

• AChR antibodies: Positive in only 50% of ocular MG
• Anti-MuSK antibodies: Occasionally positive
• Negative antibodies don't rule out ocular MG

Electrodiagnostic Testing

• Repetitive nerve stimulation
• Single-fiber EMG (most sensitive)
• May be normal in purely ocular disease

Other Tests

• CT chest (rule out thymoma)
• Thyroid function tests
• Blood tests

Treatment

Symptomatic Treatment

Pyridostigmine (Mestinon)

• First-line treatment
• Improves neuromuscular transmission
• Take 30-60 minutes before meals
• Side effects: GI cramping, diarrhea

Immunosuppression

May be needed if pyridostigmine insufficient:

• Prednisone
• Azathioprine
• Mycophenolate

Ptosis Management

• Ptosis crutches on glasses
• Eyelid tape
• Ptosis surgery in stable cases

Diplopia Management

• Prism glasses
• Occlusion (patch or frosted lens)
• Strabismus surgery if stable

Thymectomy

• Thymectomy may benefit some patients
• Especially if thymoma present
• Role in purely ocular MG still debated

Progression Risk

About 50% of patients with ocular myasthenia develop generalized myasthenia within 2 years:

Factors suggesting higher risk:

• Positive AChR antibodies
• Abnormal repetitive nerve stimulation
• Thymoma on imaging
• Older age at onset

If still purely ocular at 2 years, risk of generalization is low.

Living with Ocular Myasthenia

Managing Fatigue

• Schedule rest breaks
• Avoid sustained reading/screen time
• Use audiobooks
• Position reading material at eye level

Driving Considerations

• Double vision may affect driving
• Discuss with doctor
• May need prism glasses or patching

Activity Modifications

• Avoid extreme heat
• Adequate sleep important
• Stress management helpful

When to Seek Urgent Care

Frequently Asked Questions

Will my ocular myasthenia become generalized?

About half of patients develop generalized symptoms within 2 years. If you remain purely ocular after 2 years, the risk of progression is much lower but not zero.

Why are my antibody tests negative?

About 50% of patients with ocular myasthenia have negative antibody tests. This doesn't mean you don't have the disease—the diagnosis can be made clinically.

Can I still drive?

This depends on whether your double vision is controlled with prisms, patching, or medication. Discuss with your doctor and follow local regulations.

Is myasthenia gravis hereditary?

No, myasthenia gravis is not directly inherited. However, there may be some genetic susceptibility to autoimmune diseases in general.