Figure 2.

Illustration of the screen coverage metric, showing the division of the screen area into upper, central and lower regions (dashed lines). The central region occupies a 256 × 256-pixel square at the centre of the 512 × 512-pixel screen area (solid line). An additional 100-pixel margin (shown by the outer bounding box) was allowed for gaze points measured outside the screen area; this was incorporated into the upper or lower region, as appropriate. Superimposed is the pattern of gaze over the entire video duration for a single reader (Reader 11) viewing the same case (Case 3) under different prevalence conditions: 20% (left panel), 50% (middle panel) and 80% (right panel).