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Gaze entropy reflects surgical task load



Task (over-)load imposed on surgeons is a main contributing factor to surgical errors. Recent research has shown that gaze metrics represent a valid and objective index to asses operator task load in non-surgical scenarios. Thus, gaze metrics have the potential to improve workplace safety by providing accurate measurements of task load variations. However, the direct relationship between gaze metrics and surgical task load has not been investigated yet. We studied the effects of surgical task complexity on the gaze metrics of surgical trainees.


We recorded the eye movements of 18 surgical residents, using a mobile eye tracker system, during the performance of three high-fidelity virtual simulations of laparoscopic exercises of increasing complexity level: Clip Applying exercise, Cutting Big exercise, and Translocation of Objects exercise. We also measured performance accuracy and subjective rating of complexity.


Gaze entropy and velocity linearly increased with increased task complexity: Visual exploration pattern became less stereotyped (i.e., more random) and faster during the more complex exercises. Residents performed better the Clip Applying exercise and the Cutting Big exercise than the Translocation of Objects exercise and their perceived task complexity differed accordingly.


Our data show that gaze metrics are a valid and reliable surgical task load index. These findings have potential impacts to improve patient safety by providing accurate measurements of surgeon task (over-)load and might provide future indices to assess residents’ learning curves, independently of expensive virtual simulators or time-consuming expert evaluation.

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We thank the Tobii Group for the EyeTrackAwards Stipend awarded to LLDS, and the IAVANTE staff (Andalusian Public Foundation for Progress and Health) for their help during the data collection. This study was funded by the Campus of International Excellence (BioTic Granada) Research Programme (Research Project V7-2015 to CDP). The project was approved by the Talentia Postdoc Program launched by the Andalusian Knowledge Agency, co-funded by the European Commission’s 7th Framework Programme for Research and Technological Development—Marie Skłodowska-Curie actions—and the Andalusian Department of Economy, Innovation, Science and Employment (COFUND—Grant Agreement No. 267226 to LLDS). Research by LLDS is funded by the BBVA Foundation Program for Research, Innovation, and Cultural Creation (Grant No. 2015-2). CDP is supported by a UGR Postdoctoral Fellowship (2013 University of Granada Research Plan). Research by AC is funded by a Spanish Ministry of Economy and Competitiveness grant (PSI2012-39292 to AC). Research by LLDS, CDP, and AC is funded by a Spanish Department of Transportation grant (SPIP2014-1426 to LLDS).

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Correspondence to Leandro L. Di Stasi or Carolina Diaz-Piedra.

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Leandro L. Di Stasi, Carolina Diaz-Piedra, Héctor Rieiro, José M. Sánchez Carrión, Mercedes Martin Berrido, Gonzalo Olivares, and Andrés Catena have no conflicts of interest or financial ties to disclose.

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Leandro L. Di Stasi and Carolina Diaz-Piedra have contributed equally to this work.

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Di Stasi, L.L., Diaz-Piedra, C., Rieiro, H. et al. Gaze entropy reflects surgical task load. Surg Endosc 30, 5034–5043 (2016).

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  • Eye metrics
  • Neuroergonomics
  • Surgical skills assessment
  • Patient safety
  • Saccades