Pervasive Ocular Tremor in Patients With Parkinson Disease

Figure 1. Normal oculomotor behavior contrasted with tremulous fixations in patients with Parkinson disease (PD). A, Recordings from a control subject demonstrate stable fixations. B-D, In distinction, in representative medicated (B and C) and unmedicated (D) patients with PD, fixations are unstable anddominated by ocular tremor. Black circles represent horizontal eye movements, with positive values indicating rightward eye movements, while red triangles indicate rotational head movement along the azimuth.

Figure 2. Root mean square (RMS) velocity and absolute velocity during fixation for the control and Parkinson disease (PD) groups. Oscillatory fixation instability in patients with PD results in a greater RMS velocity (A) and absolute velocity (B) of the eye during fixation. Middle bars inside the boxes represent sample means, while the edges of the boxes indicate first and third quartiles. Bottom and top bars represent minimum and maximum, respectively. Circles denote outliers, while an asterisk denotes an extreme outlier.

Figure 3. Fixation variability for comparison between the control and Parkinson disease (PD) groups. The illustrated data consist of all sample points from 1 randomly selected fixation per subject (n = 94 fixations in medicated patients with PD and 45 control fixations), located at the origin, and with duration of at least 250 milliseconds. Note the major ocular fixation instability in patients with PD compared with the stable clustering of the controls.

Figure 4. The product of peak velocity and duration vs amplitude of saccades for the medicated patients with Parkinson disease (PD) and controls. Regression line formulae and correlation indicate no differences between the PD and control groups in the dynamics of reflexive saccades made to randomly displaced targets.