title: Detection of Changes in Surgical Difficulty: Evidence From Pupil Responses.
abstract: BACKGROUND
  Assessing the workload of surgeons requires technology to continuously monitor surgeons' behaviors without interfering with their performance. We investigated the feasibility of using eye-tracking to reveal surgeons' response to increasing task difficulty.
  
  
  METHODS
  A controlled study was conducted in a simulated operating room, where 14 subjects were required to perform a laparoscopic procedure that includes 9 subtasks. The subtasks could be divided into 3 types with different levels of task difficulty, calculated by the index of task difficulty (ID) proposed by Fitts in 1954. Pupillary responses of subjects in performing the procedure were recorded using Tobii eye-tracking equipment. Peak pupil dilation and movement time were compared between subtasks with different IDs as well as between fast moving and slow aiming phases within each subtask.
  
  
  RESULTS
  When the task difficulty was increased, task completion time increased. Meanwhile, the subjects' peak pupil size also increased. As the entire procedure was performed continuously, we found that pupil responses were not only affected by the ID in the current subtask but also influenced by subtasks before and after.
  
  
  CONCLUSIONS
  Decomposing a surgical procedure into meaningful subtasks and examining the surgeon's pupil response to each subtask enables us to identify the challenging steps within a continuous surgical procedure. Psychomotor evidence on surgeon's performance may lead to an innovation for designing a task-specific training curriculum.
authors.affiliation: University of Alberta, Edmonton, Alberta, Canada bin.zheng@ualberta.ca.
authors.forename: Bin
authors.initials: B
authors.lastname: Zheng
authors.affiliation: Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: Xianta
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: M Stella
authors.initials: MS
authors.lastname: Atkins
mesh_terms: D000328:Adult; D003198:Computer Simulation; D006804:Ergonomics; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006801:Humans; D010535:Laparoscopy; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D011680:Pupil / Q000502:physiology*; D066231:Surgeons / Q000706:statistics & numerical data*; D013647:Task Performance and Analysis; D016526:Workload / Q000706:statistics & numerical data*; D055815:Young Adult
keywords: Fitts’ law; eye-tracking; human factors in surgery; psychomotor; surgical simulation; workload assessment