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Ann Surg. 2014 Apr;259(4):824-9. doi: 10.1097/SLA.0000000000000260.

Saccadic eye movement metrics reflect surgical residents' fatigue.

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  • 1*Department of Neurobiology, Barrow Neurological Institute, Phoenix, AZ †Cognitive Ergonomics Group, Mind, Brain, and Behavior Research Center (CIMCYC), University of Granada, Granada, Spain ‡Joint Center University of Granada-Spanish Army Training and Doctrine Command, Spain §Department of Neurosurgery, Barrow Neurological Institute, Phoenix, AZ ¶St. Joseph's Hospital and Medical Center, Phoenix, AZ ‖Learning, Emotion and Decision Group, Mind, Brain, and Behavior Research Center (CIMCYC), University of Granada, Granada, Spain.



Little is known about the effects of surgical residents' fatigue on patient safety. We monitored surgical residents' fatigue levels during their call day using (1) eye movement metrics, (2) objective measures of laparoscopic surgical performance, and (3) subjective reports based on standardized questionnaires.


Prior attempts to investigate the effects of fatigue on surgical performance have suffered from methodological limitations, including inconsistent definitions and lack of objective measures of fatigue, and nonstandardized measures of surgical performance. Recent research has shown that fatigue can affect the characteristics of saccadic (fast ballistic) eye movements in nonsurgical scenarios. Here we asked whether fatigue induced by time-on-duty (~24 hours) might affect saccadic metrics in surgical residents. Because saccadic velocity is not under voluntary control, a fatigue index based on saccadic velocity has the potential to provide an accurate and unbiased measure of the resident's fatigue level.


We measured the eye movements of members of the general surgery resident team at St. Joseph's Hospital and Medical Center (Phoenix, AZ) (6 males and 6 females), using a head-mounted video eye tracker (similar configuration to a surgical headlight), during the performance of 3 tasks: 2 simulated laparoscopic surgery tasks (peg transfer and precision cutting) and a guided saccade task, before and after their call day. Residents rated their perceived fatigue level every 3 hours throughout their 24-hour shift, using a standardized scale.


Time-on-duty decreased saccadic velocity and increased subjective fatigue but did not affect laparoscopic performance. These results support the hypothesis that saccadic indices reflect graded changes in fatigue. They also indicate that fatigue due to prolonged time-on-duty does not result necessarily in medical error, highlighting the complicated relationship among continuity of care, patient safety, and fatigued providers.


Our data show, for the first time, that saccadic velocity is a reliable indicator of the subjective fatigue of health care professionals during prolonged time-on-duty. These findings have potential impacts for the development of neuroergonomic tools to detect fatigue among health professionals and in the specifications of future guidelines regarding residents' duty hours.

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