Ocular Myasthenia Gravis: Signs, Tests and Treatment
Last updated: October 2026
Ocular myasthenia gravis causes variable ptosis and diplopia with normal pupils. It mimics almost any ocular motility problem, so think of it whenever signs fluctuate.
Clinical clues
- Ptosis and diplopia that are variable and fatigable, worse in the evening; pupils always normal.
- Signs: fatigue on sustained upgaze, Cogan's lid twitch, enhancement of ptosis (lifting one lid makes the other drop), orbicularis weakness ("peek sign").
- Any pattern of ophthalmoplegia, including pseudo-INO; the pupil-sparing third nerve palsy look-alike is a classic trap.
- About half of patients with purely ocular symptoms develop generalised disease, mostly within 2 years.
Tests
| Test | Comment |
|---|---|
| Ice pack test | Ice on the lid for 2 minutes; improvement of 2 mm or more supports MG. Quick and safe in clinic |
| Sleep or rest test | Ptosis improves after 30 minutes of rest with eyes closed |
| Acetylcholine receptor antibodies | Positive in about 50% of ocular MG and 85% of generalised MG |
| Anti-MuSK and anti-LRP4 antibodies | In seronegative patients; MuSK MG often bulbar |
| Single-fibre EMG | Most sensitive test (orbicularis or frontalis), but not specific |
| Repetitive nerve stimulation | Decremental response; less sensitive in ocular MG |
| CT or MRI of the chest | For thymoma in all confirmed patients |
| Thyroid function | Thyroid eye disease coexists in some patients |
Treatment
- Pyridostigmine 30–60 mg every 4–6 hours helps ptosis more than diplopia.
- Low-dose oral corticosteroids, increased slowly, control diplopia and may reduce generalisation (EPITOME trial); steroid-sparing agents such as azathioprine for long-term use.
- Thymectomy for thymoma, and for generalised AChR-positive MG in younger adults (MGTX trial).
- Prisms, occlusion and lid crutches for symptoms; strabismus or ptosis surgery only after a long stable period.
Drugs that can worsen MG: aminoglycosides, fluoroquinolones, macrolides (telithromycin), beta-blockers (including timolol drops in some patients), magnesium, and botulinum toxin. Warn patients that breathing or swallowing difficulty is an emergency (myasthenic crisis).
Related: tests for blepharoptosis, nerve palsies, INO, thyroid eye disease.
Key sources
- Benatar M et al. Efficacy of prednisone for the treatment of ocular myasthenia (EPITOME): a randomized, controlled trial. Muscle Nerve 2016;53:363–9
- Wolfe GI et al. Randomized trial of thymectomy in myasthenia gravis (MGTX). N Engl J Med 2016;375:511–22
- Narayanaswami P et al. International consensus guidance for management of myasthenia gravis: 2020 update. Neurology 2021;96:114–22
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