TROPICAMIDE EYEDROPS CANNOT BE USED FOR RELIABLE DIAGNOSIS OF ALZHEIMERS-DISEASE

Objective: To evaluate the mydriatic effect of tropicamide eyedrops as a diagnostic test for Alzheimer's disease. Material and Methods: In a double-blind, placebo-controlled study, we assessed pupillary respons es in 22 normal control subjects, 23 patients with probable Alzheimer' s disease, 4 patients with isolated memory difficulty, and 6 patients with non-Alzheimer's dementia. Three separate studies were performed, the second and third on a subset of the original group. With use of in frared binocular pupillography, after 5 minutes of dark adaptation, we averaged pupil size during a 1-minute interval for baseline determina tions. We then instilled 0.01% tropicamide into one eye. In the first two studies, we averaged pupil size for a 1-minute period at 5-minute intervals for 30 minutes, followed by a pupil light reflex test. In th e third study, we measured pupil size every 5 minutes for 45 minutes a nd omitted the light reflex test. Results: No significant difference w as noted in pupil dilatation between normal subjects and patients with Alzheimer's disease and between patients with non-Alzheimer's dementi as and the Alzheimer's disease group in all three studies. Furthermore , on reperformance of the test in the same patients, more than 50% cha nged from a group above or below 13% pupil dilatation (a cutoff report ed to distinguish Alzheimer's disease from normal control subjects) to the opposite group. Conclusion: Results of this study indicate that p upil measurement after instillation of tropicamide cannot be used as a reliable diagnostic test for Alzheimer's disease. Moreover, test-rete st reliability with use of dilute tropicamide eyedrops is questionable .