Drop the Alzheimer's drop test

Ever since the initial report by Scinto¹ describing the use of 0.01% tropicamide as a clinical test for the early detection of Alzheimer's disease, I and my mentors (Drs. Irene Loewenfeld and H. Stanley Thompson) have been reluctant, without data of our own, to declare an opinion. According to our view then (and now), time would be the most fair judge. Table 1 summarizes this test of time; it shows the literature to date on the Alzheimer's tropicamide drop test. The table speaks loudly and its message is clearer than any argument that can be made in an editorial. Of the 19 published studies on the tropicamide test, a total of 392 patients with Alzheimer's dementia and 498 healthy control subjects have been tested (not including the additional subjects with other forms of dementia tested in some of these studies). In only one study have the authors concluded that the tropicamide mydriasis test is a clinically useful diagnostic test for Alzheimer's disease.

Anyone about to place a foot into the clinical or research waters involving the pharmacologic response of the iris should watch out for their toes, as the sharks swim in the shallows here. When it comes to measuring the pupil's reaction to topically applied drugs, high interindividual variability is the rule. Anyone who discovers that a topical mydriatic or miotic drug provides a sensitive and specific diagnostic test for a systemic or neurodegenerative disease probably has not tested enough healthy subjects. There are other difficulties common to all pupillary drug studies. Those who collect data on pupillary responses to topical drugs should …