Fluctuations in tremor at rest and eye movements during ocular fixation in subjects with Parkinson's disease.

This exploratory study investigates possible relationships between fluctuations in tremor at rest (TR) and fluctuations in eye movement amplitude during ocular fixation. TR of the hand and eye movements were analyzed in five subjects with Parkinson's disease (PD) and five age-matched controls. TR was recorded using a position laser system and eye movements were recorded using an infrared reflectometry technique (Ober2). TR amplitudes were significantly larger in the group of subjects with PD than in the control group (p</=0.01). In addition, subjects with PD showed more fluctuations in their TR (p</=0.01). Eye movements did not present more fluctuations in amplitude during ocular fixation (p>/=0.05). Changes in TR amplitude were not systematically correlated with modifications of eye movement amplitude in either group. However, occasional but distinct monocular oscillations were found in subjects with PD. Coherence values between frequencies of TR from the tested hand (3.5-7Hz) and frequencies of oscillatory eye movements (within the same frequency band) were clearly higher for the eye ipsilateral to the side of the body most affected by the disease in three subjects with PD. It is believed that these monocular oscillations may be a consequence of PD. Results from two previously published exploratory studies are integrated with the present results and new avenues of research are proposed.