OMG

Q: Which of the following is the most prominent symptom of Ocular Myasthenia Gravis (OMG)?

A) diplopia

B) lagophthalmus

C) "curtaining" of the contralateral eyelid 

D) anisocoria 

E) failure of pupillary light reflex

Answer: A

Due to fatigue of rectus muscles, diplopia and ptosis are the most common presenting symptom of OMG. Diplopia is usually binocular means present only with both eyes open. The easiest and most reliable (80% efficacy) test at the bedside is to perform an 'ice test.' Ptosis usually improves after putting ice on the upper lid. Ice should be applied for 60 seconds. The improvement lasts only a few seconds but strongly favors the diagnosis of OMG. Ice test may also improve diplopia.

All other choices (B, C, D, and E) are rare in OMG.

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References: 

1. Chatzistefanou KI, Kouris T, Iliakis E, et al. The ice pack test in the differential diagnosis of myasthenic diplopia. Ophthalmology 2009; 116:2236.

2. Averbuch-Heller L, Poonyathalang A, von Maydell RD, Remler BF. Hering's law for eyelids: still valid. Neurology 1995; 45:1781.

3. BAPTISTA AG, SILVA E SOUZA H. Pupillary abnormalities in myasthenia gravis. Report of a case. Neurology 1961; 11:210.

4. Cooper J, Pollak GJ, Ciuffreda KJ, et al. Accommodative and vergence findings in ocular myasthenia: a case analysis. J Neuroophthalmol 2000; 20:5.