[The pupillary response test as a method to differentiate various types of dementia]

Pupillometry is a non-invasive measurement technique based on the pupillary response to specific sensoric, mental and emotional variables. After topical application of a cholinergic antagonist (tropicamide) an increased pupillary dilatation response in Alzheimers s disease patients was described ("receptor test"). The aim of the present study was to evaluate the usefulness of the 0.01% tropicamide receptor test in differentiating types of dementia.

425 patients (159 men, 266 women, mean age 75 years) of the Memory Clinic of the SMZ Ost Vienna, Austria were included in the study. 195 patients suffered from a dementia in Alzheimer's disease with late onset (ICD-10: F00.1), 42 from dementia in Alzheimer's disease with early onset (F00.0), 71 from vascular dementia (F01), 34 from Lewy-Body dementia (F03) and 83 from mixed dementia (F00.2). All patients were investigated by means of a computer-assisted pupillometer. The pupillary diameter of the left eye was measured 4 times (baseline=0 minutes, after 20, 40 and 60 minutes). 4 minutes after baseline one drop of 0.01% tropicamide solution was installed onto the left eye of the patients.

At baseline the pupillary diameter was largest in Lewy-Body dementia, smallest in vascular dementia. Significant differences were observed between vascular dementia and early-onset dementia in Alzheimer's disease as well as between Lewy-Body dementia and all other dementia syndromes (except dementia in Alzheimer's disease with early onset). The 0.01% tropicamide receptor test made it possible to differentiate early-onset dementia in Alzheimer's disease from vascular and mixed dementia.

Utilizing pupillometry in combination with the 0.01% tropicamide receptor test allows to discriminate between different dementia types of, as demonstrated in our study.