Objective: This study aims to investigate variations in antisaccade parameters (latency, damping ratio, peak velocity, and amplitude) among different stages of Parkinson’s Disease (PD), Progressive Supranuclear Palsy (PSP), and healthy controls (HC).

Background: Saccades are rapid eye movements between fixation points. Antisaccades involve looking away from a direct stimulus, testing voluntary eye control and are known to be impaired in neurological conditions such as PD and PSP. Quantifying such performance impairments could serve as valuable indicators for diagnosis and progression in these diseases.

Method: Using infrared oculometry, antisaccades were recorded from 124 participants: 11 early-stage unmedicated Parkinson’s Disease (PD) patients, 51 early-stage medicated PD patients, 18 advanced-stage medicated PD patients, 9 Progressive Supranuclear Palsy (PSP) patients, and 35 age-matched healthy controls (HC). Analysis included 6347 correct antisaccades, examining latency, peak velocity, and amplitude. The damping ratio was derived using a second-order system model. Linear mixed-effects models assessed group differences. Post-hoc tests compared estimated marginal means across groups using the Tukey method for multiple comparisons. Standardized effect sizes were calculated using the pairwise method, with the model’s residual standard deviation as the standardizer.

Results: PSP patients exhibited significant impairments in antisaccade performance compared to HC, with increased latency (p=0.0024, effect size=1.3), reduced peak velocity (p=0.02, effect size=1.08), and decreased amplitude (p=0.019, effect size=0.993). Early-stage medicated PD patients showed significantly lower latency than PSP (p=0.0024, effect size=-1.3). The damping ratio showed no significant effect.

Conclusion: The significantly increased latency, reduced peak velocity, and decreased amplitude in PSP patients, coupled with large effect sizes, highlight the potential of these antisaccade metrics as diagnostic biomarkers for differentiating PSP from PD and HC. These findings contribute to our understanding of the distinct ocular motor signatures of PSP and PD. Future studies with larger sample sizes and longitudinal designs are warranted to validate these findings and explore their potential applications in clinical settings.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/linear-mixed-effect-modelling-of-antisaccades-in-parkinsons-disease-and-progressive-supranuclear-palsy/