Eye-Tracking Assessment of Visual, Oculomotor, and Pupillary Biomarkers During Reading in Parkinson's Disease

Parkinson's disease (PD) is associated with visual, cognitive, and oculomotor alterations that may impair reading, highlighting the potential of eye tracking to objectively characterise these changes during a task. An observational study included 46 patients with PD, classified according to the Hoehn and Yahr (HY) scale, and 56 age- and sex-matched healthy controls. All participants underwent a comprehensive optometric examination and performed the Radner-Vissum reading test at 50 cm, while eye movements were recorded using a portable eye tracker. Fixation, saccadic, pupil diameter, and reading performance variables were analysed. PD patients showed a progressive reduction in pupil diameter (p = 0.001) and saccadic alterations, with reduced amplitude and velocity at the initial visual acuity levels (p < 0.001), whereas fixation parameters did not differ significantly between groups (p > 0.05). They also showed longer reading times, greater total reading time (84.33 ± 30.39 s vs. 37.50 ± 7.23 s; p < 0.001), lower overall scores (p < 0.001), and more reading errors (p < 0.001), whereas the logarithmic reading acuity determination (logRAD) values were comparable (p = 0.905). Overall, PD was associated with impaired reading performance and oculomotor and autonomic nervous system changes objectively measured by eye tracking during functional reading.