Eye movement parameters and cognitive functions in Parkinson's disease patients without dementia

Background: Cognitive deficits and eye movement abnormalities have been demonstrated to be detectable early clinical manifestations of Parkinson's disease. Understanding the relationship between these phenotypes may yield insight into the underlying anatomical pathways, assisting in the search for simple non-invasive markers of early neurodegeneration.

Objective: To explore the correlations between eye movement parameters with multi-domain cognitive functions in patients suffering from Parkinson's disease without dementia.

Method: This is a cross-sectional case-control study of Parkinson's disease patients without dementia. Participants underwent global and domain-specific cognitive tests and an eye-tracking visual search task to characterize eye movement parameters.

Results: 62 Chinese Parkinson's disease patients without dementia and 62 sex-, age- and education-matched controls were recruited. The disease group performed worse in multiple cognitive tasks and exhibited a smaller saccadic amplitude. Negative correlations between the eye fixation duration and performance in semantic verbal fluency, verbal and visual recognition memory tasks were observed, though there was no moderation effect on the correlations due to the presence of Parkinson's disease. A common cholinergic deficit in the temporal and parietal regions may account for the observed correlations. The lack of association with predominantly frontal-executive tasks may suggest specificity of these correlations.

Conclusion: Prolonged visual fixation duration is correlated with poorer performance in semantic verbal fluency, verbal and visual recognition memory tasks in Parkinson's disease patients without dementia, although these correlations are not specific. The clinical utility of eye movement parameters as an early marker for cognitive decline in Parkinson's disease warrants further exploration in longitudinal studies.