What is the treatment for ocular myasthenia?

Treatment of Ocular Myasthenia Gravis

Start with pyridostigmine 30 mg orally three times daily, gradually increasing to a maximum of 120 mg four times daily, but recognize that approximately 50% of patients with ocular myasthenia show minimal response and will require escalation to corticosteroids. 1, 2

First-Line Treatment: Pyridostigmine

• Begin pyridostigmine at 30 mg orally three times daily and titrate upward based on symptom response, with a maximum dose of 120 mg four times daily 1, 3
• Pyridostigmine is FDA-approved for myasthenia gravis and works by inhibiting acetylcholinesterase at the neuromuscular junction 2
• However, only about 50% of patients with ocular myasthenia respond adequately to pyridostigmine alone, particularly those with strabismus and diplopia 1, 4
• Ocular symptoms are highly variable and not readily remedied with prisms, making pharmacologic escalation often necessary 1

Second-Line Treatment: Corticosteroids

If pyridostigmine fails to adequately control ptosis and diplopia, add prednisone using an alternate-day regimen, as 66-85% of patients respond positively to corticosteroids. 1, 5

• Corticosteroids demonstrate superior efficacy (66-85% response rate) compared to pyridostigmine's 50% response rate 1, 3
• Start prednisone at 0.5 mg/kg orally daily if symptoms interfere with activities of daily living 1
• Critical pitfall: Increase steroid doses slowly to avoid precipitating myasthenic crisis 6
• After achieving symptom control, taper slowly to the lowest effective dose 6
• Use alternate-day regimen when possible to minimize side effects 5

Third-Line Treatment: Steroid-Sparing Agents

• Add azathioprine if corticosteroids fail to provide adequate control, if high steroid doses are required, or if steroids are contraindicated 1, 5
• Azathioprine serves as a steroid-sparing agent and can be used for long-term maintenance 5, 7
• Mycophenolate mofetil is an alternative for patients intolerant of azathioprine 7, 8

Essential Workup After Diagnosis

• Obtain CT chest with contrast to evaluate for thymoma, which occurs in 10-20% of AChR-positive patients 1
• If thymoma is present, thymectomy is mandatory 1, 5
• For ocular myasthenia without thymoma, thymectomy remains controversial and is not routinely recommended 5, 6

Adjunctive and Supportive Measures

• Ice pack test (apply over closed eyes for 2 minutes) can temporarily reduce ptosis and diplopia, useful both diagnostically and for temporary symptom relief 1, 3, 4
• Occlusive devices, prisms, and eyelid supports may provide symptomatic relief 6
• Strabismus surgery should only be considered after disease stabilization, typically requiring 2-3 years of medical treatment 1, 4

Critical Medication Avoidance

Immediately review and discontinue medications that worsen myasthenia, including β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolide antibiotics. 1, 3

Monitoring for Disease Progression

• 50-80% of patients with initial ocular symptoms develop generalized myasthenia within a few years 1, 3
• Regular neurologic assessment is essential to detect early signs of generalization 4
• Monitor for respiratory symptoms, dysphagia, and proximal limb weakness 1
• Pulmonary function testing with negative inspiratory force and vital capacity should be performed if generalization is suspected 1

Refractory Cases

• For AChR-positive patients refractory to conventional therapy, efgartigimod alfa-fcab is FDA-approved 1
• IVIG (2 g/kg IV over 5 days) or plasmapheresis can be considered for severe cases, though rarely needed for purely ocular disease 1, 8

Multidisciplinary Collaboration

• Management requires collaboration between an experienced ophthalmologist and neurologist 1, 3, 4