Eye tracking to support assessment of patients with prolonged disorder of consciousness - a case series.

Objective: To investigate if eye tracking can support detection of covert voluntary eye movements and to compare these findings with a simultaneously performed clinical assessment according to the Coma Recovery Scale manual regarding visual stimuli.

Design: Observational case series.

Subjects: Twelve outpatients with prolonged disorders of consciousness recruited from the rehabilitation clinic of a regional rehabilitation unit.

Method: Eye movements were recorded with a wearable eye tracker while performing 4 test items from the Coma Recovery Scale Revised. The clinical assessment and recorded eye movement responses were analysed for agreement.

Results: Response data was obtained from 238 out of 288 trials. Eye-tracking data were obtained in median 89.6% of the trials (37.5-100%). The eye tracking assessment judged a significantly higher percentage of trials as a response (46.2%) compared with the clinical assessment (18.1%), mainly in test items "visual pursuit" and "visual fixation".

Conclusion: Eye tracking showed potential to be more effective in the detection of putative voluntary eye movements compared with conventional examination. Based on the findings in this and previous studies, eye tracking may serve as a useful complementary tool when examining patients with prolonged disorders of consciousness.