Objective: It is important to know what potential confounding effects the medications used to treat Parkinson’s disease (PD) have on eye movement, in order to understand whether they will be a useful measure in patients who are medicated.

Background: Oculomotor function has been proposed as a biomarker for PD. Many studies have focused on saccadic eye movements, which are affected by PD in several ways; for example, PD prolongs prosaccadic latency. The literature in this area is mixed, with some studies suggesting medication prolongs latency and others indicating that it is shortened. In this study, we describe the effects of levodopa on saccades in medicated PD subjects at the early to mid stages of the disease.

Methods: Participants for this study were part of the OxQUIP (Oxford Quantification in Parkinsonism) study cohort. Horizontal saccadic eye movements were measured using an infra-red, head-mounted Saccadometer. Thirty-eight PD patients were evaluated in medication on and off conditions, together with conventional clinical assessments under the same conditions. Thirty-four Healthy controls, mostly the spouses of the PD patients, also performed the same protocol.

Results: As expected, the UPDRS motor score significantly improved after taking levodopa. Administration of levodopa significantly increased prosaccadic latency in PD subjects.

Conclusions: PD prolongs prosaccadic latency, and while levodopa attenuates the motor features of the disease, it lengthens latency further. If saccades are to be used to track disease progression it is critical that longitudinal measurements are taken in the same medication state.

References: 1. Yugeta A, Terao Y, Fukuda H, Ugawa Y. Effects of levodopa on saccade performance in Parkinson’s disease. Movement Disorders 2008;23(1):S296-S297. 2. Antoniades CA, Demeyere N, Kennard C, Humphreys GW, Hu MT. Antisaccades and executive dysfunction in early drug-naive Parkinson’s disease: The discovery study. Movement Disorders 2015;30(6):843-847.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/using-saccades-as-an-early-test-of-levodopa-treatment-in-parkinsons-disease/