Objective: To investigate the differential effects of levodopa versus pramipexole on eye-tracking parameters in treatment-naïve patients with Parkinson’s disease.

Background: Parkinson’s disease (PD) is characterized by progressive neurodegeneration affecting motor function, with oculomotor disturbances representing an early and quantifiable manifestation of the disease. Eye-tracking technology provides a non-invasive method to measure these visual-motor impairments. While levodopa and dopamine agonists such as pramipexole are standard treatments for PD motor symptoms, their differential effects on oculomotor function remain incompletely understood, particularly in treatment-naïve patients.

Method: Eleven newly diagnosed drug-naïve PD patients meeting MDS diagnostic criteria were enrolled and pseudo-randomized into two treatment arms: levodopa or pramipexole. Each patient underwent identical assessments at three timepoints: baseline (pre-treatment), 1-month, and 3-month follow-up. The levodopa group received a titration schedule of 0mg → 50mg TID → 300mg TID, while the pramipexole group followed a regimen of 0mg → 1.05mg (XR, base) OD → 2.1mg (XR, base) OD. All assessments were conducted during ON phases, beginning with an eye-tracking protocol (prosaccades and antisaccades) followed by neuropsychological evaluation.

Results: At the 1-month follow-up, performance on the numerical Stroop task deteriorated in both groups, evidenced by extended reaction times for inhibiting prepotent responses, with no significant between-group differences. By the 3-month follow-up, a significant increase in express prosaccades (EP) percentage was observed, with a notable interaction between measurement timepoint and medication group. Specifically, patients treated with pramipexole exhibited a significantly higher percentage of express prosaccades compared to levodopa-treated patients.

Conclusion: Dopamine agonists appear to affect oculomotor control differently than levodopa, with pramipexole associated with more prepotent oculomotor responses. The increased prevalence of express prosaccades in pramipexole-treated patients may indicate reduced inhibitory control in frontostriatal circuits, potentially serving as a measurable marker of medication-specific effects on executive function.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/comparing-the-impact-of-levodopa-versus-pramipexole-on-eye-tracking-parameters-in-treatment-naive-parkinsons-disease-a-longitudinal-study/