Objective: To report qualitative analysis of smooth pursuit (SP) abnormalities found in early Parkinson´s disease (PD) patients using one- and two-dimensional test.

Background: The eye movements abnormalities associated to PD are the result of underlying changes due to the pathological condition. Given their close relationship, the possibility of using them as early detection biomarkers of the disease is often described in literature. One of such eye movements is SP, which is often studied by analyzing the observation of a patient that follows a target stimulus, which moves in the horizontal or vertical axis alone. Nevertheless, prior clinical studies do not address the potential of using target stimulus moving in the two-dimensional space or exploit the potential of different target velocities or amplitudes during the analysis.
Since different neurological pathways are involved for the generation of SP in each axis, we hypothesise that two-dimensional SP establish a more realistic and complex scenario which might lead to the identification of more robust biomarkers of the disease.

Method: 106 participants with ages between 40 and 80 y-o were included: 54 controls and 52 PD patients, with 3 or less years since motor symptoms onset. Video-oculography was employed for tracking the eye movements and recording them. A battery of 12 SP tests were performed: 4 in the horizontal axis, 4 in the vertical axis, and 4 following two-dimensional patterns.

Results: In contrast to 1-Dimensional patterns, the PD group shows that the oculographic sequences obtained in the four 2-Dimensional tests that were tested present a larger number of saccades. Furthermore, the analysis of the data, reveals participants presenting saccadic pursuit patterns in 2D tests, while no events of this type were present on 1D tests for the same participant.

Conclusion: These results suggest that an evaluation based on two-dimensional SP tests could significantly improve the sensitivity of the analysis as it allows the detection of events that can be not detected by one-dimensional test. Further quantitative analysis will be performed to support these results.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/two-dimensional-smooth-pursuit-tests-for-early-parkinsons-disease-identification/