Quantitative analysis of pursuit ocular movements in Parkinson's disease by using a video-based eye tracking system

The purpose of this study is to assess the efficacy and the tolerability of a new vision-based non-intrusive eye tracker in a population composed of normal controls and in patients affected by nonadvanced Parkinson's disease (PD). PD patients characteristically have difficulty in sustaining repetitive motor actions. Previous studies showed a progressive bradykinesia and hypokinesia of pursuit ocular movements (POM) in advanced PD. We found that the values of POM were lower in PD patients than in normal controls (p < 0.001). In PD patients, the values correlated closely with Hoehn and Yahr stage and Unified Parkinson Disease Rating Scale motor subscore (p < 0.001, for both). Our data suggest that deficit in POM occurs also in nonadvanced PD patients and it is closely correlated with clinical scores. Thus, this vision-based system can be considered a new method to provide, noninvasively, measures of POM dysfunctions and can be used as reliable indices of disease severity in PD patients.