Introduction: Various fields have used gaze behaviour to evaluate task proficiency. This may also apply to surgery for the assessment of technical skill, but has not previously been explored in live surgery. The aim was to assess differences in gaze behaviour between expert and junior surgeons during open inguinal hernia repair.
Methods: Gaze behaviour of expert and junior surgeons (defined by operative experience) performing the operation was recorded using eye-tracking glasses (SMI Eye Tracking Glasses 2.0, SensoMotoric Instruments, Germany). Primary endpoints were fixation frequency (steady eye gaze rate) and dwell time (fixation and saccades duration) and were analysed for designated areas of interest in the subject's visual field. Secondary endpoints were maximum pupil size, pupil rate of change (change frequency in pupil size) and pupil entropy (predictability of pupil change). NASA TLX scale measured perceived workload. Recorded metrics were compared between groups for the entire procedure and for comparable procedural segments.
Results: Twenty-five cases were recorded, with 13 operations analysed, from 9 surgeons giving 630 min of data, recorded at 30 Hz. Experts demonstrated higher fixation frequency (median[IQR] 1.86 [0.3] vs 0.96 [0.3]; P = 0.006) and dwell time on the operative site during application of mesh (792  vs 469  s; P = 0.028), closure of the external oblique (1.79 [0.2] vs 1.20 [0.6]; P = 0.003) (625  vs 448  s; P = 0.032) and dwelled more on the sterile field during cutting of mesh (716  vs 268  s; P = 0.019). NASA TLX scores indicated experts found the procedure less mentally demanding than juniors (3  vs 12 [5.2]; P = 0.038). No subjects reported problems with wearing of the device, or obstruction of view.
Conclusion: Use of portable eye-tracking technology in open surgery is feasible, without impinging surgical performance. Differences in gaze behaviour during open inguinal hernia repair can be seen between expert and junior surgeons and may have uses for assessment of surgical skill.