Methodological aspects of using a wearable eye-tracker to support diagnostic clinical evaluation of prolonged disorders of consciousness.
Jan Johansson, Kristina Franzon, Alison K Godbolt and 1 others
PMID 34037240WHAT IT FOUND
Wearable eye-tracking was feasible for assessing consciousness in four patients.
In most disagreements with clinical scores, the tracker detected responses the clinicians missed. This suggests it might uncover hidden consciousness, but the study was too small to prove it works.
Key findings
01Eye-tracking data was successfully retrieved from a high percentage of trials for three of the four patients, with agreement rates between 54% and 80% compared to clinical assessment.
02When clinical and eye-tracking assessments disagreed, the eye-tracking data indicated a positive response in 81% of cases, suggesting it may detect conscious responses missed by standard observation.
03Calibration was often difficult or impossible due to strabismus, requiring work-arounds like analysing relative gaze changes instead of absolute positions.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study included only four patients, which is far too small to determine if eye-tracking is more accurate than clinical assessment. The primary goal was feasibility, not diagnostic validity, so the results show the technology *can* be used, not that it *should* be used. Calibration frequently failed due to strabismus, a common condition in this population, limiting the use of standard analysis tools. One patient had data for only 21% of trials, showing the method is unreliable for patients with extreme gaze deviations. The analysis relied heavily on visual inspection of data plots rather than robust statistical methods, introducing potential observer bias.
Declared interests
The authors declared no conflicts of interest. The study was approved by the Swedish Ethical Review Authority.
The easy way to misread this
Do not conclude that eye-tracking is a superior or validated diagnostic tool for consciousness. This was a small feasibility study of four patients. The finding that trackers detected responses clinicians missed suggests potential, but it has not been proven to be more accurate than standard assessment, and technical issues like calibration failure remain significant barriers.