Eye Trace is an editing technique that anticipates where the audience's eyes will be looking within the frame at any moment so that the filmmaker can use this knowledge to direct where, when, and what the audience will look at in a frame, especially across multiple cuts.
When looking at a new frame, the first place human eyes are to things that are different or have changed. This tendency is especially true if something on-screen is
Brighter
Larger
In-Focus
Moving
Eyes
Mouth
As an editor, understanding where the audience is looking when a cut happens can help determine how long it might take them to process story information from the shot. It can also hide discontinuity, especially if it happens in a part of the frame that the editor knows the audience's eye should not be looking at in that moment.
A few common ways to catch the viewers' eyes:
Motion: This could be a movement by the actor leading your eye to a particular spot on the screen.
Position: Placing characters at the edge of the frame, then cutting to a shot of another character on the same edge where the viewer's eyes live at that moment, knowing that will be the first place their eyes shift.
Color: Add a bright or different color within the frame, whether a prop or wardrobe, to make an object stand out or evoke a specific emotion.
After the audience notices the item that catches their eye, they will then move their focus around the screen.