Saccade, Pupil, and Blink Responses in Rapid Eye Movement Sleep Behavior Disorder.

Background Parkinson's disease (PD) patients exhibit deficits in saccade performance, pupil function, and blink rate. Isolated REM (rapid eye movement) Sleep Behavior Disorder (RBD) is a harbinger to PD making them candidates to investigate for early oculomotor abnormalities as PD biomarkers. Objectives We tested whether saccade, pupillary, and blink responses in RBD were similar to PD. Methods RBD (n = 22), PD (n = 22) patients, and healthy controls (CTRL) (n = 74) were studied with video-based eye-tracking. Results RBD patients did not have significantly different saccadic behavior compared to CTRL, but PD patients differed from CTRL and RBD. Both patient groups had significantly lower blink rates, dampened pupil constriction, and dilation responses compared to CTRL. Conclusion RBD and PD patients had altered pupil and blink behavior compared to CTRL. Because RBD saccade parameters were comparable to CTRL, pupil and blink brain areas may be impacted before saccadic control areas, making them potential prodromal PD biomarkers. © 2021 International Parkinson and Movement Disorder Society.