Edrophonium test in myasthenia: quantitative oculography.

The response of eye movements to edrophonium is easily missed by clinical observation alone. Binocular horizontal ten degree saccades were recorded by infrared oculography, whilst the vision of one eye was occluded, before and after fatigue repeated intravenous injection of dilute edrophonium, and fatigue induced during anticholinesterase inhibition by intravenous edrophonium, in 26 patients with diplopia or ptosis of uncertain aetiology. The most reliable criterion of a positive response was an increase in the amplitude of the saccades of the fixating eye by 10% or more after each of several injections of dilute edrophonium. The response was positive in 13 patients and was difficult to observe clinically when the responses of the saccades of the eyes moving conjugately were unequal and when the patient presented with ptosis and no diplopia. Edrophonium infrared oculography proved to be a sensitive test for weakness due to the neuromuscular junction defect of myasthenia gravis affecting extraocular muscles.