Video Pupillometric Evaluation of the Pupillary Reflex as a Test for the Clinical Manifestations of Parkinson’s Disease

Abstract

Purpose. The aim was to investigate the utility of the eye-tracking pupillary reflex when testing for autonomic dysfunction in Parkinson’s disease (PD) patients by correlating the results with clinical status.
Methods. The eye-tracking video pupillometric evaluation of the pupillary reflex to light and the isometric hand grip task were measured in 45 PD patients (Hoehn & Yahr stage, 2-4; mean age, 72.7 ± 9.9 years; disease duration 7.2 ± 5.0 years; male, 53.3%). We performed consecutive measurements of pupil size, which were expressed as the number of pixels, and measured the light miosis response (LMiR) and light mydriasis response (LMyR) to changes in luminance (80 Lux and 400 Lux). We also calculated the mydriasis response to the isometric hand grip task (HMyR) as ratios to the pupil size before the stimulus.
Results. LMiR and LMyR were significantly smaller in PD patients than in controls (p = 0.002 and p = 0.006, respectively). Pupil size before and after the hand grip task and HMyR were similar to normal control values. LMiR in PD patients significantly correlated with Movement Disorder Society-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) part 3 (p = 0.011) and part 4 (p = 0.003). LMyR correlated with MDS-UPDRS part 4 (p = 0.016). HMyR correlated with disease duration (p = 0.007) and levodopa equivalent daily dose (p = 0.025). Multiple linear regression analyses demonstrated that MDS-UPDRS part3 (p = 0.005) was significantly associated with LMiR. Disease duration (p = 0.037) was significantly associated with LMyR. But there was no clinical factor associated with HMyR.
Conclusion. An abnormal pupillary reflex, such as a low response to light stimulation and a high response to the hand grip task, may be observed in the advanced stage of PD.