EMDR Effects on Pursuit Eye Movements

This study aimed to objectivize the quality of smooth pursuit eye movements in a standard laboratory task before and after an Eye Movement Desensitization and Reprocessing (EMDR) session run on seven healthy volunteers. EMDR was applied on autobiographic worries causing moderate distress. The EMDR session was complete in 5 out of the 7 cases; distress measured by SUDS (Subjective Units of Discomfort Scale) decreased to a near zero value. Smooth pursuit eye movements were recorded by an Eyelink II video system before and after EMDR. For the five complete sessions, pursuit eye movement improved after their EMDR session. Notably, the number of saccade intrusions—catch-up saccades (CUS)—decreased and, reciprocally, there was an increase in the smooth components of the pursuit. Such an increase in the smoothness of the pursuit presumably reflects an improvement in the use of visual attention needed to follow the target accurately. Perhaps EMDR reduces distress thereby activating a cholinergic effect known to improve ocular pursuit

The smooth pursuit task.

<p>(A) Spatial arrangement for smooth pursuit: one white dot on the black computer screen, 57 cm from subject's eyes, moving from center to right or left (15°), randomly. (b) Temporal arrangement: the white dot moves to opposite direction to the pursuit then returns to center (200 ms) to begin pursuit, the stimulus at velocity of 15°/s. (c) Typical recording of normal rightward pursuit is obtained by averaging the position signal of the two eyes (LE+RE)/2; CUS indicates catch-up saccades during the pursuit.</p

Parameters of pursuit eye movements.

<p>Individual mean values with their standard deviation of number of CUS (A), amplitude of CUS (B) and gain of pursuit (C); data are shown before and after EMDR for smooth pursuit to right. Group mean values are presented on the right of each group. Asterisks show statistically significant difference.</p

SUDs and VOC before and after EMDR.

<p>SUDs and VOC before and after EMDR.</p

Eye movements recorded during the pursuit task.

<p>Individual traces of leftward smooth pursuit eye movements before and after EMDR for each subject. Each trace shows the instantaneous eye position over time during an individual trial. The thick diagonal line shows target displacement from centre to the left of the screen. The eye movement starts after a latency period (thick horizontal segment, s2). The eye position lagging behind target position frequently small catch up saccades are made (downward arrows). Occasionally the eye anticipates, going beyond target position and returns back (see upward arrow). All other notations as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010762#pone-0010762-g002" target="_blank">Fig. 2</a>.</p