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

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