Tracking The Disc: Clinicians Eye Movements During Optic Disc Examination

1. Evelyn C O'Neill
2. George X.Y. Kong
3. Danielle Ong
4. Michael A, Coote
5. Jonathan G. Crowston

Centre for Eye Research Australia, University of Melbourne, The Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne VIC 3002.

Purpose: In this study we sought to determine whether there are fundamental differences in visual gaze behaviour between glaucoma subspecialists and trainees during grading of glaucomatous optic disc photographs

Methods: 7 glaucoma subspecialists and 23 trainees participated in the project. All subjects were shown 8 optic disc images and eye movements were tracked with a Tobii Eyetracker to look for differences in patterns of viewing behaviour. For each disc image graders were then asked to assess disc size, vertical cup:disc ratio, rim loss, nerve fibre layer loss and the probability of glaucoma. There was no time restriction.

Results: Experienced viewers had a systematic viewing pattern and spent more time observing the most likely areas of disc pathology (superior and inferior poles of the optic nerve head and adjacent nerve fibre layer) compared to trainees. Glaucoma subspecialists spent significantly larger proportions of time examining focal areas of pathology than trainees (mean 27.7% and 12.2% of total time, P<0.05, respectively). Further, experts altered their viewing habit according to disc morphology. Overall the trainees spent longer total times looking at disc images than glaucoma subspecialist (mean 27.1 and 17.7 seconds, respectively, P<0.01) had no consistent pattern of gaze behaviour and gaze behaviour was unchanged by disc morphology.

Conclusion: Glaucoma subspecialists adopt systematic gaze behaviour when examining the optic nerve and RNFL. Teaching trainees to adopt similar gaze behaviour will now be assessed to determine if this improves glaucoma diagnosis skills.