Myasthenia Ocular Type

Ocular Myasthenia Gravis (OMG) causes eye muscle weakness, resulting in ptosis and diplopia. Treatment options include acetylcholinesterase inhibitors, immunosuppressive therapy, thymectomy, and corrective surgeries for ptosis and strabismus. Immunomodulating treatments can be considered for refractory cases.

2024-01-08 15:28:06 - Editor

Ocular Myasthenia Gravis (OMG): Introduction and Clinical Features

Occular myasthenia gravis (OMG) is an autoimmune disorder characterised by weakness and fatigability of ocular skeletal muscles including levator palpebrae superioris, orbicularis oculi and the oculomotor muscles. Patients usually present with ptosis, diplopia, or oculomotor paresis. (1, 2)

Treatment Approaches for OMG

Treatment of OMG includes symptomatic treatment, acetylcholinesterase inhibitors, immunosuppressive therapy, immunomodulatory treatment, thymectomy, and corrective treatments of ptosis and strabismus. (3)

Symptomatic Management of Ptosis and Diplopia

Symptomatic management of ptosis is with crutches and lid adhesive devices which could help in the treatment of ptosis pending a response to acetylcholinesterase inhibitors or immunosuppressive therapy. Use of lubricating drops and periods of abstinence from device use are crutial to prevent corneal dryness and exposure keratopathy. For diplopia, an eye patch, opaque contact lens or occlusion of an eyeglass lens with opaque tape are simple ways to eliminate it. Prism lenses offer another non-pharmacological alternative for patients with diplopia. (4)

Acetylcholinesterase Inhibitors for OMG

Acetylcholinesterase inhibitors include pyridostigmine (starting at 30 mg three times daily), neostigmine (starting at 15 mg three times daily). (5, 6)

Chronic Immunosuppressive Therapy for OMG

Chronic immunosuppressive therapy includes glucocorticoids (starting at 20 mg daily and then increase by 5 mg every three to five days to a usual target dose of 60 mg per day. This often takes four to eight weeks. Once an effective response is obtained, it is important not to taper the steroids too quickly. Many patients who respond to steroid can be effectively tapered down to 10 mg daily as a maintenance dose), or steroid sparing agents (azathioprine [starting at 50 mg daily], mycophenolate [starting at 500 mg twice daily]). (7, 8)

Immunomodulating Treatments for Refractory OMG

Approximately 10% of patients with severe MG are refractory to chronic immunosuppressive therapy. immunomodulating treatments including plasma exchange (a typical course of treatment consists of five exchanges [3 to 5 L of plasma each] over 7 to 14 days), intravenous immune globulin (IVIG) (the total dose is 2 g/kg, usually over five days), eculizumab (900 mg infused weekly for four weeks, followed by 1200 mg a week later, and then 1200 mg every two weeks), or rituximab (375 mg/m2 weekly for four doses) can be considered. (9)

Thymectomy in the Treatment of OMG

Thymectomy has therapeutic role in selected patients with MG. Those patients include those with thymoma. (10)

Surgical Correction for Ptosis and Diplopia in OMG

Surgical correction in the form of extraocular muscle resection and recession, can be performed on patients with stable ophthalmoparesis. (11)

References

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