Exploring Eye Movements in Patients with Glaucoma When Viewing a Driving Scene
Figure 2
Novel ‘Point of Regard’ Analysis.
Examples of the BCE ‘point of regard’ analysis superimposed on frames from some of the HPT films. The centre of the red ellipse represents the mean ‘point of regard’ of the controls with the spatial extent of the ellipse being one standard deviation from this centre along two principal axes, theoretically affording ‘coverage’ of approximately 67% of the ‘point of regard’ locations in a given frame. Note how the location and spatial extent of this ellipse changes with each frame of the film as the control subjects' view is drawn to different aspects of the changing road scene. For each frame the number of patients' points of regard (blue symbols) ‘captured’ by the ellipse can be automatically counted and compared to the expected value under the null hypothesis that the average ‘viewing area’ is the same in the two groups. Note that not all nine patients are recorded in each frame because of blinks, loss of data, and variable responses. Also, note that in the UK vehicles are driven on the left hand side of the road. See Audio/Video - S1.