Pupil reaction to light in Alzheimer’s disease: evaluation of pupil size changes and mobility

Abstract

The aim of the study is to assess pupil size changes and mobility evaluation as a diagnostic marker in patients with probable Alzheimer's disease (AD). Twenty-three control subjects and 23 patients with probable AD entered the study. The latter patients had been under observation for 2 years and had undergone all necessary examinations to verify their initial diagnosis. A full record of the pupil's reaction to light was registered. Ten parameters from these data were measured, reported and then compared in both group of subjects. Patients with probable AD had abnormal pupillary function compared with such function in healthy aging. All pupillary light reflex (PLR) variables differed significantly between the two groups (p<0.005) except baseline pupil diameter (D1) and minimum pupil diameter (D2). Maximum constriction acceleration (ACmax) was the best predictor in classifying a subject as normal or as AD with perfect classification ability (area under the curve =1, p<0.001). In addition, the correlation between the percentage recovery-redilatation (%D1) and ACmax was highly negative in the group of AD patients (r = -0.808, p<0.005). Pupil size changes and mobility examination may be a fast, non-invasive and efficient additional diagnostic marker in AD diagnosis.