The 'eye test' in recognition of late-onset Alzheimer's disease.

A rapid and specific diagnostic test for Alzheimer's disease (AD), the prevalent cause of dementia in the elderly, is currently unavailable. The aim of this study was to verify the validity of the recently proposed 'Eye Test' in the identification of AD patients, based on their supposed greater mydriatic response to cholinergic antagonists. We tested the pupillary response to the instillation of 0.01% tropicamide in 48 subjects: 15 patients with probable or possible Alzheimer's disease, five patients with vascular dementia (VD), 16 elderly controls (EC) and 12 young controls (YC). Mean pupil dilation in the treated eye at 30 and 40 min after drops instillation was not significantly different among the four groups. The mean change in anisocoria at 30 min was significantly greater in the AD group (0.90 mm, S.D. 0.83) than in the YC group (0.21 mm, S.D. 0.46), but no significant difference was found among the AD group, the EC group and the VD group. Our results, therefore, do not support the potential usefulness of the pupillary response to dilute tropicamide for identifying individuals with AD.