Brief Alert
Pupillary Dilation with Tropicamide in AD Patients
Sources: Ferrario E, et al. Is videopupillography useful in the diagnosis of Alzheimer's disease (AD)? Neurology 1998;50:642-644; Kaneyuki H, et al. Enhanced miotic response to tropical dilute pilocarpine in patients with AD. Ibid. 802-804; Kardon RH. Drop the Alzheimer's droptest. Ibid. 588-591.
Scinto et al (Science 1994;256:1051-1054) claimed a statistical difference in inducing pupillary dilation by the cholinergic antagonist, tropicamide in 14 AD patients compared against 41 controls. Regrettably, time and larger numbers of AD patients and controls have torpedoed any apparent value of the test. None of 18 subsequent reports including 378 AD patients vs. 466 controls found any statistical verification of such improvement. In fact, Ferrario et al reported that 20 patients with AD had less mydriasis following tropicamide than did 44 normal control subjects. Also, Kaneyuki et al found an opposite response to that of Scinto et al in that among 18 AD patients and 13 controls, tropicamide induced less mydriasis in the AD group. Pilocarpine, however, induced a greater miotic response in AD patients vs. controls. Kardon identifies and summarizes the 19 total published studies devoted to the tropicamide test. As he notes in a clear editorial, none but the index report were able to verify statistically the accuracy of tropicamide-induced mydriasis in AD. -fp
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