To the Editor.
—The controversy over the diagnosis of myasthenia gravis with the Tensilon (intravenous edrophonium chloride) test still rages on. We must take issue with Daroff, a friend and colleague, on his comments on the routine use of the Lancaster red-green test for diagnosing myasthenia gravis.1 Dr Daroff is a very astute clinician with a tremendous background of research experience in eye movements. Everyone agrees that immediate relief of ptosis or improvement of strabismus under direct observation are the best objective clinical means of confirming a positive response to Tensilon, but the Lancaster red-green test is not as subjective as Daroff implies. A cooperative patient merely superimposes the red and green lights, and in his mind sees only the two overlapping images. The true position of the lights is a direct objective indication of eye position. It is not a measurement of diplopia, although the patient may indeed
Younge BR, Bartley GB. Lancaster Test With Tensilon for Myasthenia. Arch Neurol. 1987;44(5):472–473. doi:10.1001/archneur.1987.00520170004005
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