To the Editor.
—Suspected ocular myasthenia is confirmed when a significant degree of ophthalmoplegia or ptosis is observed to resolve unequivocally in response to intravenous administration of edrophonium chloride. However, clinicians are sometimes confronted with patients who have intermittent symptoms and mild or ambiguous signs. In such patients, the criteria for establishing a positive response to the conventional edrophonium test may be difficult to determine. The patient with a motility disturbance but no ptosis also constitutes a diagnostic dilemma, since administration of edrophonium can strengthen some muscles more than others, resulting in a persistent deviation that masks the positive response.1 For example, a small exotropia might be converted to a small esotropia. Intramuscular neostigmine methylsulfate may be useful in evaluating some patients with only a motility disturbance since its prolonged duration of action allows the physician sufficient time to compare premedication binocular motility measurements with those obtained in response
Jacobson DM. Edrophonium Tonography in Suspected Ocular Myasthenia. Arch Ophthalmol. 1987;105(9):1174-1175. doi:10.1001/archopht.1987.01060090032014