To the Editor.
—I read with interest the article by Kardon et al1 on the use of the cocaine test in the diagnosis of Horner's syndrome. Their study supports the fact that cocaine can distinguish a patient with Horner's syndrome from a patient without. The major emphasis of their article is that the degree of physiologic anisocoria after instillation of cocaine provides a better prediction of Horner's syndrome than the actual change of anisocoria noted between the precocaine and postcocaine conditions. They note that with a 1.0-mm anisocoria after cocaine instillation, the odds of having Horner's syndrome were 5990 to 1.Although this odds ratio may be valid for their study, in which the control population had no anisocoria, I believe it may be misleading. Clinically, one rarely has to distinguish between normal pupils, as in their control patients with no anisocoria, and Horner's syndrome. In practice, one must
Moster ML. The Cocaine Test and Horner's Syndrome. Arch Ophthalmol. 1990;108(12):1667. doi:10.1001/archopht.1990.01070140021005