In this study, the intentional poor performance on testing (“sandbagging”) on the King–Devick test was evaluated by measuring eye movement of non-concussed patients under normal performance conditions and intentional poor performance.

Findings show that the intentional poor performance on baseline testing can be detected by objective eye movement measurement.
– Kathleen F. Freeman, OD, FAAO

Written by Leonard J. Press OD, FAAO, FCOVD
The King–Devick Test (KDT) has emerged as a quick and relatively inexpensive test to administer to athletes as a potential sideline test for concussion. This saccadic eye movement test based on rapid naming of randomly spaced numbers in sequence is useful in helping determine when an athlete is capable of returning to play. It is predicated on the availability of baseline scores and the slowing of test scores (by a mean of 4.8 s) when administered to the athlete who is suspected of being concussed. The challenge of course is that most athletes want to return to play and may therefore purposely try to slow down or “sandbag” their baseline score so that their visual cognitive impairment when concussed is not as apparent. In this crossover study, athletes were advised on one test administration to give their best effort and on another trial to sandbag their attempt. The mean best-effort KDT time of 48.2 s with a range between 33.9 and 60.1 s was consistent with baseline KDT times in healthy athletes in the literature, whereas the mean time with sandbagging attempts was 41.5 s with a range between 2.5 and 174.5 s on the sandbagging. This suggests that credible sandbagging is difficult to perform. As the article concludes, objective eye movement recordings may further help to identify athletes attempting to sandbag the KDT at baseline.

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