Objective: To characterize eye movements during reading in patients with moderate stage Parkinson’s disease (PD) with respect to medication state and cognitive ability.

Background: Many patients with PD complain about visual symptoms which often lead to functional impairment in activities of daily life, like reading texts. From an eye movement perspective, reading consists of serial fixations as well as forwards and regressive saccades. Since PD saccades are known to be hypometric and tend to show a prolonged latency in cognitively impaired PD patients, those factors may contribute to reading performance.

Methods: Eye movements of 19 PD patients (mean age 66.1±8.4, disease duration 4.8±3.7, levodopa equivalent dose 547±207) in ON and OFF medication state and 13 healthy controls (HC, age 69.4±3.9) were recorded during reading of a text (assessing number, duration, amplitude of fixations, progressive and regressive saccades). Additionally, motor (Unified Parkinson’s Disease Rating Scale part III, UPDRS) and general cognitive performance (Montreal Cognitive Assessment, MoCA) were assessed.

Results: PD patients read significantly less words per minute (WPM, OFF: p=0.009) than controls due to an increased number of regressive saccades (p<0.05) and longer mean fixation duration (p<0.05). All those variables showed correlation to MoCA score (fixation duration: p<0.01, R2=0.46) in PD, while there were no correlations to age, levodopa equivalent dose or UPDRS. Disease duration was correlated to WPM (OFF: p<0.01) and to the mean and standard deviation of regression amplitudes in OFF (p<0.001). Levodopa did not significantly change any reading-related variables.

Conclusions: Slower reading speed in PD is mainly caused by higher number of regressive saccades and increased fixation durations which are related to cognitive rather than motor dysfunction. Levodopa seems not to improve reading performance in PD sufficiently which is important knowledge in counseling patients with functional oculomotor complaints.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/eye-movements-during-reading-in-parkinsons-disease-a-pilot-study/