Gaze presents the problem of accidental selections: users can look at things but, without an explicit way to indicate selections, gaze would be selecting the first interactive object the cursor hovers on.
To avoid this problem and being certain the user wants to select a given option, gaze can be coupled with fusing.
Fusing is a way of letting users confirm a choice by hovering over it for an interval of time.
Cursor change and hover state
When using fusing, the gaze cursor changes if hovering on an interactive element, usually turning into a ring.
There are two indications of affordance: one is the cursor changing shape and the other is provided by the object, which usually changes state when hovered by gaze.
The cursor also provide feedback about the duration of the fusing, which then determines the selection.
Fusing can be cancelled by moving away from the element. This should have the effect of resetting the timer as well.
Advantages and disadvantages of fusing
Fusing accentuates the fact that the gaze cursor is not necessarily where the user is looking.
Gaze in fact tracks the position of the head.
This can lead to accidental selections if the point of focus of gaze and what users are looking at is different.
It is important to consider the position of UI elements when using fusing.
These should allow users to rest the cursor in a neutral area, preventing accidental clicks.
Related to: Targeting with gaze